YANj 


pgr 


AGKIC,  C 


LIBRARY 
COLLEGE  OF 
AGRICULTURE 
Berkeley.  Cal. 


LILRARY 
COLLEGE  OF 

AN  V   AGRICULTURE 

Berkeley.  Cal. 


INTRODUCTION  TO  THE  STUDY 


COMPOUNDS  OF  CARBON 


OB, 


OEGAJSTIC  OHEMISTET. 


BY 

IRA  REMSEN, 

PROFESSOR  OF    CHEMISTRY  IN  THE   JOHNS   HOPKINS   UNIVERSITY. 


BOSTON: 
D.   C.   HEATH   &   COMPANY. 

1889. 


Entered  according  to  Act  of  Congress,  in  the  year  1885,  by 

IRA   REMSEN, 
in  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


PRINTED    BY 

BERWICK  &  SMITH, 
BOSTON,  U.S.A. 


PREFACE. 


fT^HIS  book  is  intended  for  those  who  are  beginning  the  subject. 
For  this  reason,  special  care  has  been  taken  to  select  for 
treatment  such  compounds  as  best  serve  to  make  clear  the 
fundamental  principles.  General  relations  as  illustrated  by  special 
cases  are  discussed  rather  more  fully  than  is  customary  in  books 
of  the  same  size ;  and,  on  the  other  hand,  the  number  of  com- 
pounds taken  up  is  smaller  than  usual.  The  author  has  endeav- 
ored to  avoid  dogmatism,  and  to  lead  the  student,  through  a 
careful  study  of  the  facts,  to  see  for  himself  the  reasons  for 
adopting  the  prevalent  views  in  regard  to  the  structure  of  the 
compounds  of  carbon.  Whenever  a  new  formula  is  presented, 
the  reasons  for  using  it  are  given  so  that  it  may  afterward  be 
used  intelligently.  It  is  believed  that  the  book  is  adapted  to 
the  needs  of  all  students  of  chemistry,  whether  they  intend 
to  follow  the  pure  science,  or  to  deal  with  it  in  its  applica- 
tions to  the  arts,  medicine,  etc.  It  is  difficult  to  see  how, 
without  some  such  general  introductory  study,  the  technical 
chemist  and  the  student  of  medicine  can  comprehend  what  is 
usually  put  before  them  under  the  heads  of  "  Applied  Organic 
Chemistry "  and  "  Medical  Chemistry." 

Without  some  direct  contact  with  the  compounds  considered, 
it  is  difficult  to  get  a  clear  idea  regarding  them  and  their 
changes.  A  course  of  properly  selected  experiments,  illustrating 
the  methods  used  in  preparing  the  principal  classes  of  com- 
pounds, and  the  fundamental  reactions  involved  in  their  trans- 
formations, wonderfully  facilitates  the  study.  The  attempt  has 

3G8813 


iv  PREFACE. 

been  made  to  give  directions  for  such  a  course.  More  than 
eighty  experiments  which  could  be  performed  in  any  chemical 
laboratory  are  described ;  and  it  is  hoped  that  the  plan  may 
meet  with  approval.  The  time  required  to  perform  a  fair  pro- 
portion of  these  experiments  is  not  great;  and  the  results  in  the 
direction  of  enlarging  the  student's  knowledge  of  chemical  phe- 
nomena, will,  it  is  firmly  believed,  furnish  a  full  compensation 
for  the  time  spent. 

The  order  in  which  the  topics  are  taken  up  will  be  found  to 
differ  somewhat  from  that  commonly  adopted.  The  object  in  view 
was,  however,  not  to  find  a  new  method,  but  to  find  one  which 
would  bring  out  as  clearly  as  possible  the  beauty  and  simplicity 
of  the  relations  which  exist  between  the  different  classes  of  car- 
bon compounds.  The  reasons  for  the  method  used  are  given  in 
the  body  of  the  book. 


CONTENTS. 

CHAPTER   I. 

Introduction. 

PAGE. 

Sources  of  compounds.  —  Purification  of  the  compounds.  —  Deter- 
mination of  the  boiling-point.  —  Determination  of  the  melting- 
point.  —  Analysis.  —  Formula.  —  Structural  formula.  —  General 
principles  of  classification  of  the  compounds  of  carbon  ...  1 

CHAPTER  II. 

Methane  and  Ethane. —Homologous  Series. 
Methane.  —  Ethane 20 

CHAPTER  III. 

Halogen  Derivatives  of  Methane  and  Ethane. 
Substitution.  —  Chloroform.  —  lodoform.  —  Di-chlor- ethanes.  — 


Isomerism 


CHAPTER   IV. 
Oxygen  Derivatives  of  Methane  and  Ethane. 

Alcohols.  —  Methyl  alcohol.  —  Ethyl  alcohol.  —  Fermentation.  — 
Ethers.  —  Ethyl  ether.  —  Mixed  ethers.  —  Aldehydes.  —  For- 
mic aldehyde.  —  Acetic  aldehyde.  —  Paraldehydc.  —  Metalde- 
hyde.  —  Chloral.  —  Acids.  —  Formic  acid.  —  Acetic  acid.  — 
Ethereal  salts.  —  Ketones.  —  Acetone 34 


VI  CONTENTS. 

CHAPTER   V. 

Sulphur  Derivatives  of  Methane  and  Ethane 
Mercaptans.  —  Sulphur  ethers.  —  Sulphouic  acids 74 

CHAPTER    VI. 

Nitrogen  Derivatives  of  Methane  and  Ethane. 

Cyanogen.  —  Hydrocyanic  acid.  —  Cyanides.  —  Cyanuric  acid.  — 
Sulpho-cyanic  acid.  —  Cyanides.  —  Isocyanides  or  cafbamines. 
—  Cyanates  and  isocyanates.  —  Sulpho-cyanates.  —  Isosulpho- 
cyanates  or  mustard  oils.  —  Substituted  ammonias.  —  Hydra- 
zine  compounds.  —  Nitro-compounds.  —  Nitroso-  and  isonitro- 
so-compounds  .  .  .  .  , 79 

CHAPTER  VII. 

Derivatives  of  Methane  and  Ethane  containing  Phos- 
phorus, Arsenic,  etc. 

Phosphorus  compounds.  —  Arsenic  compounds.  —  Zinc  ethyl.  — 
Sodium-ethyl.  —  Retrospect 103 

CHAPTER  VIII. 
The  Hydrocarbons  of  the  Marsh-Gas  Series,  or  Paraffins. 

Petroleum.  —  Synthesis  of  paraffins.  —  Isomerism  among  the  paraf- 
fins.—Hexanes  .  .  108 

CHAPTER   IX. 

Oxygen  Derivatives  of  the  Higher  Members  of  the 
Paraffin  Series. 

Alcohols.  —  Normal  propyl  alcohol.  —  Secondary  propyl  alcohol.  — 
Secondary  alcohols.  —  Butyl  alcohols.  —  Pentyl  alcohols.  — 
Aldehydes.  —  Acids.  —  Fatty  acids.  —  Propionic  acid.  —  Bu- 


CONTENTS.  Vll 

PAGE. 

tyric  acids.  —  Valeric  acids.  —  Palmitic  acid.  —  Stearic  acid. 
—  Soaps.  —  Polyacid  alcohols  and  polybasic  acids. — Di-acid 
alcohols.  —  Ethylene  alcohol  or  glycol.  —  Bibasic  acids.  — 
Oxalic  acid.  —  Malonic  acid.  —  Succinic  acids.  —  Pyrotartaric 
acid.  —  Tri-acid  alcohols.  —  Glycerin.  — Ethereal  salts  of  gly- 
cerin. —  Fats.  —  Tri-basic  acids.  —  Tetr-acid  alcohols.  —  Pent- 
acid  alcohols.  —  Hex-acid  alcohols  .  .  120 


CHAPTER  X. 
Mixed  Compounds.  —  Derivatives  of  the  Paraffins. 

Hydroxy-acids.  —  Carbonic  acid.  —  Glycolic  acid.  —  Lactic  acids. 

—  Hydroxy-acids,  CnH2n04.  —  Glyceric  acid.  —  Hyclroxy-acids, 
CnHsn-sOs.  —  Tartronic  acid.  —  Malic  acid.  —  Hydroxy-acids, 
CnH2n-206. —  Mesoxalic  acid.  —  Tartaric  acid.  —  Racemic  acid. 

—  Inactive  tartaric  acid.  —  Hydroxy-acids,  CnH2n-4O7.  —  Citric 
acid.  —  Hydroxy-acids,  CnH2n_2O8. —  Saccharic  acid.  —  Mucic 
acid 155 

CHAPTER  XI. 
Carbohydrates. 

The  glucose  group.  —  Dextrose.  —  Levulose.  —  Galactose.  —  The 
cane  sugar  group.  —  Cane  sugar.  —  Sugar  of  milk.  —  Maltose. 

—  The  cellulose  group.  —  Cellulose.  —  Gun  cotton.  —  Paper.  — 
Starch.  —  Dextrin.  —  Gums 177 

CHAPTER  XII. 
Mixed  Compounds  containing  Nitrogen. 

Amido-acids.  —  Amido-formic  acid.  —  Glycocoll.  —  Sarcosine.  — 
Amido-propionic  acids.  —  Leucine.  —  Amido-sulphonic  acids. 

—  Taurine.  —  Cyan-amides.  —  Guanidine.  —  Creatine.  — Urea 
or  carbamide  and  derivatives.  —  Substituted  ureas.  —  Para- 
banic  acid.  — Oxaluric  acid.  —  Barbituric  acid.  —  Sulpho  urea. 


Vlll  CONTENTS. 

PAGE 

—  Uric  acid.  —  Xanthine.  —  Theobromine.  —  Caffeine.  —  Guan- 
ine.  —  Retrospect 190 


CHAPTER  XIII. 

Unsaturated  Carbon  Compounds.  —  Distinction  between 
Saturated  and  Unsaturated  Compounds. 

Ethylene   and    its    derivatives.  —  Ethyleue.  —  Alcohols,  CnH2nO. 

—  Allyl   alcohol.  —  Allyl   mustard  oil.  —  Acrolem.  —  Acids, 
CnH2n-202.  —  Acrylic  acid.  —  Crotonic  acid.  —  Oleic  acid.  — 
Polybasic  acids  of  the  ethylene  group.  —  Acids,  C2H.2(CO2H)2. 

—  Acids,  C5H6O4. —  Aconitic  acid.  —  Acetylene  and  its  deriva- 
tives. —  Acetylene.  —  Propargyl  alcohol.  —  Acids,  CnH2n-402. 

—  Propiolic  acid.  —  Tetrolic  acid.  —  Sorbic  acid. — Leinole'ic 
acid.  —  Valylene.  —  Dipropargyl 208 

CHAPTER  XIV. 

The  Benzene  Series  of  Hydrocarbons.  —  Aromatic 
Compounds. 

Benzene.  —  Toluene.  —  Xyleues.  —  Ethyl-benzene.  —  Mesitylene.  — 
Pseudocumene.  —  Cymene 230 

CHAPTER  XV. 

Derivatives  of  the  Hydrocarbons,  CnEfen-e,  of  the 
Benzene  Series. 

Halogen  derivatives  of  benzene.  —  Bibrom-benzene.  —  Halogen 
derivatives  of  toluene.  —  Halogen  derivatives  of  the  higher 
members  of  the  benzene  series.  — Nitro  compounds  of  benzene 
and  toluene.  —  Mono-nitro-beuzene. — Dinitro-benzene. — Nitro- 
toluenes.  —  Amido  compounds  of  benzene,  etc.  —  Aniline.  — 
Toluidines.  —  Diazo  compounds  of  benzene.  —  Sulphonic  acids 
of  benzene.  —  Phenols,  orhydroxyl  derivatives  of  benzene,  etc. 

—  Mon-acid  phenols.  —  Phenol.  —  Tri-nitro-phenol.  —  Phenyl 
mercaptan.  —  Cresols.  —  Thymol.  —  Di-acid  phenols.  —  Pyro- 


CONTENTS.  IX 

PAGE. 

catechin.  —  Resorcin.  —  Styphnic  acid.  —  Hydroquinone.  — 
Orcin.  —  Tri-acid  phenols.  —  Pyrogallol.  —  Alcohols  of  the 
benzene  series.  — Benzyl  alcohol.  —  Aldehydes  of  the  benzene 
series.  —  Oil  of  bitter  almonds.  —  Cuminic  aldehyde.  —  Acids 
of  the  benzene  series.  —  Monobasic  acids,  CnH^n-sCV  — Ben- 
zoic  acid.  —  Substitution  products  of  benzoic  acid.  —  Isatine. 

—  Hippuric  acid.  —  Toluic  acids.  —  a-Toluic  acid.  —  Oxindol. 

—  Mesitylenic   acid.  —  Hydro-cinnamic   acid.  —  Hydro-carbo- 
styril.  —  Bibasic  acids,   CnH2n-io04.  —  Phthalic    acid.  —  Iso- 
phthalic  acid.  —  Terephthalic  acid.  —  Hexabasic  acid.  —  Mel- 
litic  acid.  —  Phenol-acids,   or   Hydroxy-acids  of  the  benzene 
series.  —  Salicj^lic  acid.  —  Oxybenzoic  acid.  —  Para-oxybenzoic 
acid.  —  Anisic  acid.  —  Di-hydroxy -benzoic   acid's,  C7H6O4.  — 
Protocatechuic    acid.  —  Vanillic    acid.  —  Vanillin.  —  Tri-hy- 
clroxy-benzoic  acids,  C7H605.  —  Gallic  acid.  —  Tannic  acid.  — 
Ketones  and  allied  derivatives  of  the  benzene  series.  —  Qui- 
nones.  —  Pyridine  bases.  —  Pyridine.  —  Terpenes.  —  Camphor.  252 

CHAPTER  XVI. 

Di-phenyl-methane,  Tri-phenyl-methane,  Tetra-phenyl- 
methane,  and  their  Derivatives. 

Tri-phenyl-methane.  —  Aniline   dyes.  —  Para-rosaniline.  —  Rosani- 

line. — Phthaleins. — Phenol-phthalei'ns. — Fluoresce'in. — Eosin.  313 

CHAPTER   XVII. 

Hydrocarbons,  CnH2n-8,  and  Derivatives. 
Styrene.  —  Styryl  alcohol.  —  Cinnamic  acid.  —  Coumarin      .     .     .  323 

CHAPTER  XVIII. 

Phenyl-acetylene  and  Derivatives. 

Phenyl-acetylene.  —  Phenyl-propiolic    acid.  —  Ortho-nitro-phenyl- 
propiolic  acid.  —  Indigo  and  allied  compounds.  —  Indigo-blue. 

—  Indigo-white   ....  .  328 


CONTENTS. 


CHAPTER  XIX. 

Hydrocarbons  containing  two  Benzene  Residues  in 
Direct  Combination. 

PAGE. 

Diphenyl.  — Naphthalene.  —  Quinoline  and  analogous  compounds.  333 


CHAPTER  XX. 

Hydrocarbons  containing  two  Benzene  Residues  in 
Indirect  Combination. 

Anthracene.  —  Authraquinoue.  —  Alizarin.  —  Purpurin.  —  Phenan- 

threne  .  346 


CHAPTER  XXI. 
Glucosides.  —  Alkaloids,  etc. 

Aesculin.  —  Amygdalin.  —  Tannins.  —  Helicin.  —  Indican.  —  My- 
ronic  acid.  —  Salicin.  —  Saponin.  —  Alkaloids.  —  Quinine.  — 
Ciuchonine.  —  Cocaine.  —  Nicotine.  —  Morphine.  —  Narcotine. 
—  Piperine.  —  Piperidine.  —  Strychnine 352 


INDEX   .  ,    .    ,  , 357 


OHEMISTEY 

OF    THE 

COMPOUNDS    OF    CARBON, 


CHAPTER  I. 

INTRODUCTION. 

IN  studying  the  compounds  of  carbon,  we  cannot  fail  to 
be  struck  by  their  large  number,  and  by  the  ease  with  which 
they  undergo  change  when  subjected  to  various  influences. 
Mainly  on  account  of  the  large  number,  though  partly  on 
account  of  peculiarities  in  their  chemical  conduct,  it  is  custom- 
ary to  consider  these  compounds  by  themselves.  At  first, 
General  Chemistry  was  divided  into  Inorganic  and  Organic 
Chemistry,  as  it  was  believed  that  there  were  fundamental 
differences  between  the  compounds  included  under  the  two 
heads.  Those  compounds  which  form  the  mineral  portion  of 
the  earth  were  treated  under  the  first  head,  while  those  which 
were  found  ready  formed  in  the  organs  of  plants  or  animals 
were  the  subject  of  organic  chemistry.  It  was  believed  that, 
as  the  organic  compounds  are  elaborated  under  the  influence  of 
the  life  process,  there  must  be  something  about  them  which 
distinguishes  them  from  the  inorganic  compounds  in  whose  for- 
mation the  life  process  has  no  part.  Gradually,  however,  this 
idea  haw  been  abandoned ;  for,  one  by  one,  the  compounds 
which  are  found  in  plants  and  animals  have  been  made  in  the 
chemical  laboratory,  and  without  the  aid  of  the  life  process. 
The  first  instance  of  the  preparation  of  an  organic  compound 
by  an  artificial  method  was  that  of  urea.  This  substance 
was  obtained  by  Wohler  in  1828  from  ammonium  cyanate. 
When  a  water  solution  of  the  latter  is  allowed  to  evaporate,  urea 


is  deposited.  Up  to  the  time  of  Wohler's  discovery,  the 
formation  of  urea,  like  that  of  other  organic  compounds,  was 
thought  to  be  intimately  and  necessarily  connected  with  life ; 
but  it  was  thus  shown  that  it  could  be  formed  without  the  inter- 
vention of  life.  Afterward,  it  was  shown  that  potassium 
cyanide  can  be  made  by  passing  nitrogen  over  a  heated  mixture 
of  carbon  and  potassium  carbonate  ;  and,  as  potassium  cyanate 
can  be  made  from  the  cyanide  by  oxidation,  it  follows  that 
urea  can  be  made  from  the  elements.  Finally,  in  1856,  Berthe- 
lot  succeeded  in  making  potassium  formate  by  passing  carbon 
monoxide  over  heated  potassium  hydroxide  ;  and  in  making 
acetylene,  a  compound,  the  composition  of  which  is  represented 
by  the  formula  C2H2,  by  passing  electric  sparks  between  elec- 
trodes of  carbon  in  an  atmosphere  of  hydrogen.  Since  that 
time,  every  year  has  witnessed  the  artificial  preparation,  by 
purely  chemical  means,  of  compounds  of  carbon  which  are  found 
in  the  organs  of  plants  and  animals. 

It  hence  appears  that  the  formation  of  the  compounds  of 
carbon  is  not  dependent  upon  the  life  process  ;  that  they  are 
simply  chemical  compounds  governed  by  the  same  laws  that 
govern  other  chemical  compounds ;  and  the  name,  Organic 
Chemistry,  signifying,  as  it  does,  that  the  compounds  included 
under  it  are  necessarily  related  to  organisms,  is  misleading. 
Organic  chemistry  is  nothing  but  the  Chemistry  of  the  Com- 
pounds of  Carbon.  It  is  not  a  science  independent  of  inorganic 
chemistry,  but  is  just  as  much  a  part  of  chemistry  as  the  chem- 
istry of  the  compounds  of  sodium,  or  of  the  compounds  of 
silicon,  etc. 

The  name  Chemistry  of  the  Compounds  of  Carbon  has  been 
objected  to  as  being  too  broad.  Strictly  speaking,  this  title 
includes  the  carbonates,  and  it  is  customary  to  treat  of  these 
widely  distributed  substances  under  the  head  of  Inorganic 
Chemistry.  Most  books  on  Inorganic  Chemistry  also  deal  with 
some  of  the  simpler  compounds  of  carbon,  such  as  the  oxides, 
cyanogen,  marsh  gas,  etc. 


SOURCES    OF    COMPOUNDS.  6 

This  objection  is  of  weight  only  as  far  as  the  carbonates 
are  concerned,  and  it  does  not  appear  strong  enough  to  make 
the  introduction  of  a  new  name  necessary.  It  should  be  men- 
tioned, however,  that  the  name  Chemistry  of  the  Hydrocarbons 
and  their  Derivatives  has  recently  been  suggested.  The  exact 
significance  of  this  name  will  appear  when  the  compounds  with 
which  we  shall  have  to  deal  come  up  for  consideration. 

Sources  of  compounds. — The  compounds  of  carbon  are, 
for  the  most  part,  made  in  the  laboratory ;  but  in  preparing 
them  we  usually  start  with  a  few  fundamental  compounds 
which  are  formed  by  natural  processes.  A  large  number,  such 
as  the  sugars,  starch,  cellulose,  and  the  alkaloids,  of  which 
morphine,  quinine,  and  nicotine  are  examples,  occur  ready 
formed  in  plants,  but  always  mixed  with  other  substances. 
Others,  such  as  urea,  uric  acid,  albumin,  etc.,  occur  in  animal 
organisms.  Petroleum,  which  has  been  formed  in  Nature  by 
processes  intimately  connected  with  those  which  give  rise  to  the 
formation  of  coal,  contains  a  large  number  of  compounds  con- 
sisting of  onl}7  carbon  and  hydrogen ;  and  these  compounds 
serve  as  the  starting-points  in  the  preparation  of  a  large  number 
of  derivatives.  When  coal  is  heated  for  the  purpose  of  manu- 
facturing illuminating  gas,  a  very  complex  mixture  of  liquid 
and  solid  products  is  obtained  as  a  by-product,  knowrn  as  coal 
tar.  This  substance  yields  some  of  the  most  valued  compounds 
of  carbon.  A  larger  number  of  the  compounds  of  carbon  are 
obtained  from  this  than  from  any  other  one  source.  When 
bones  are  heated  in  the  manufacture  of  bone-black,  an  oil 
known  as  bone  oil  is  obtained.  Of  late,  this  has  proved  to 
be  the  source  of  a  large  number  of  interesting  compounds. 
In  the  preparation  of  charcoal  by  heating  wood,  the  liquid  pro- 
ducts are  sometimes  condensed,  and  they  form  the  source  of 
several  important  compounds,  among  which  may  be  mentioned 
wood  spirits  or  methyl  alcohol,  acetone,  and  pyroligneous  or 
acetic  acid. 


4  INTRODUCTION. 

Finally,  we  are  dependent  upon  the  process  known  as  fer- 
mentation for  a  number  of  the  most  important  compounds  of 
carbon.  Fermentation,  as  will  be  shown,  is  a  general  term, 
signifying  any  process  in  which  a  change  in  the  composition  of 
a  body  is  effected  by  means  of  minute  animal  or  vegetable 
organisms.  The  best  known  example  of  fermentation  is  that 
of  sugar,  which  gives  rise  to  the  formation  of  ordinary  alcohol. 
Alcohol  in  turn  serves  as  the  starting-point  for  the  preparation 
of  a  large  number  of  compounds. 

Purification  of  the  compounds.  —  Before  the  natural 
compounds  of  carbon  can  be  studied  chemically,  they  must,  of 
course,  be  freed  from  foreign  substances ;  and  before  the  con- 
stituents of  the  complex  mixtures,  petroleum,  coal  tar,  and  bone 
oil  can  be  studied,  they  must  be  separated  und  purified.  The 
processes  of  separation  and  purification  are,  in  many  cases, 
extremely  difficult.  If  the  substance  is  a  solid,  different 
methods  may  be  used  according  to  the  nature  of  the  substance. 
Crystallization  is  more  frequently  made  use  of  than  any  other 
process.  This  is  well  illustrated,  on  the  large  scale,  in  the 
refining  of  sugar,  which  consists,  essentially,  in  dissolving  the 
sugar  in  water,  filtering  through  bone-black,  which  absorbs 
coloring  matter,  and  then  evaporating  down  to  crystallization. 
When  two  or  more  substances  are  found  together,  they  may,  in 
many  cases,  be  separated  by  what  is  called  fractional  crystalliza* 
tion.  This  consists  in  evaporating  the  solution  until,  on  cool- 
ing, a  comparatively  small  part  of  the  substance  is  deposited. 
This  deposit  is  filtered  off,  and  the  solution  further  evaporated ; 
when  a  second  deposit  is  obtained,  and  so  on  to  the  end.  Thu 
successive  deposits  thus  obtained  are  then  recrystallized,  each 
separately,  until,  finally,  the  deposits  are  found  to  be  homo- 
geneous. 

The  chief  solvents  used  are  water,  alcohol,  ether,  benzine, 
and  bisulphide  of  carbon ;  alcohol  being  the  most  generally 
applicable. 


PURIFICATION   OF   THE   COMPOUNDS.  5 

In  the   case  of  liquids,  the  process  of   distillation   is  used. 
The  apparatus  commonly  used  is  illustrated  in  Fig.  1 . 


B 


Fig.  1. 

The  only  part  of  the  apparatus  which  requires  explana- 
tion is  the  tube  A.  This  is  known  as  the  distilling  tube. 
It  is  simply  a  straight  glass 
tube,  about  16cm  long  and  12  to 
14mm  in  diameter,  to  which  is 
attached  a  smaller  branch  some- 
what inclined  downward.  The 
object  of  the  tube  is  to  accom- 
modate a  thermometer  B,  which 
is  so  fixed  by  means  of  a  cork, 
that  it  is  in  the  centre  of  the 
larger  tube,  and  its  bulb  directly 
opposite  the  opening  of  the 
smaller  branch. 

For  small  quantities  of  liquids, 
the  distilling  flask  is  much  used.     This  is  a  long-necked,  round 


Fig.  2. 


6  INTRODUCTION. 

flask,  with  a  branch  tube  fitted  directly  into  the  neck,  as  shown 
in  Fig.  2.  In  this  apparatus,  the  thermometer  is  fitted  into 
the  neck  of  the  flask  in  the  same  relation  to  the  exit  tube  as  in 
the  larger  apparatus. 

For  the  separation  of  liquids  of  different  boiling-points,  the 
process  of  fractional  or  partial  distillation  is  much  used.  When 
a  mixture  of  two  or  more  liquids  of  different  boiling-points  is 
boiled,  it  will  be  noticed  that  the  boiling-point  gradually  rises 
from  that  of  the  lowest  boiling  substance  to  that  of  the  highest, 
Thus,  ordinary  alcohol  boils  at  78°,  and  water  at  100°.  If  the 
two  be  mixed,  and  the  mixture  distilled,  it  will  be  found  that  it 
begins  to  boil  at  78°,  but  that  very  little  passes  over  at  this 
temperature.  Gradually,  as  the  distillation  proceeds,  the  tem- 
perature indicated  by  the  thermometer  becomes  higher  and 
higher,  until  at  last  100°  is  reached,  when  all  distils  over.  Now 
the  distillates  obtained  at  the  different  temperatures  differ  from 
each  other  in  composition.  Those  obtained  at  the  lower  tem- 
peratures are  richer  in  alcohol  than  those  obtained  at  the  higher 
temperatures,  but  none  of  them  contains  pure  alcohol  or  pure 
water.  In  order  to  separate  the  two,  therefore,  we  must  pro- 
ceed as  follows  :  A  number  of  clean,  dry  flasks  are  prepared  for 
collecting  the  distillates.  The  boiling  is  begun,  and  the  point 
at  which  the  first  drops  of  the  distillate  appear  in  the  receiver  is 
noted.  That  which  passes  over  while  the  mercury  rises  through 
a  certain  number  of  degrees  (3,  5,  or  10,  according  to  the  char- 
acter of  the  mixture)  is  collected  in  the  first  flask.  The  receiver 
is  then  changed,  without  interruption  of  the  boiling,  and  that 
which  passes  over  while  the  mercury  rises  through  another 
interval  equal  to  the  first  is  collected  in  the  second  flask.  The 
receiver  is  again  changed,  and  a  third  distillate  collected ;  and 
so  on,  until  the  liquid  has  all  been  distilled  over.  It  has  thus 
been  separated  into  a  number  of  fractions,  each  of  which  has 
passed  over  at  different  temperatures.  In  the  case  of  alcohol 
and  water,  for  example,  we  might  have  collected  distillates  from 
78°  to  83°,  from  83°  to  88°,  from  88°  to  93°,  from  93°  to  98°, 


PURIFICATION   OF   THE   COMPOUNDS.  7 

from  98°  to  100°.  Now  a  clean  distilling  flask  is  taken,  and 
into  it  introduced  the  first  fraction.  This  is  distilled  until  the 
thermometer  marks  the  upper  limit  of  the  original  first  fraction, 
the  new  distillate  being  collected  in  the  flask  which  contained  the 
first  fraction.  When  this  upper  limit  is  reached,  the  boiling  is 
stopped.  It  will  be  found  that  there  is  some  of  the  liquid  left 
in  the  distilling  flask.  That  is  to  say,  assuming  that  in  the  first 
distillation  the  first  fraction  was  collected  between  78°  and  83°, 
on  boiling  this  fraction  the  second  time  it  will  not  all  come  over 
between  these  points  ;  when  83°  is  reached  some  will  be  left  in 
the  flask.  The  second  fraction  is  now  poured  into  the  distilling 
flask  through  a  funnel  tube,  and  the  boiling  is  again  started. 
Of  the  second  fraction,  a  portion  will  pass  over  below  the  point 
at  which  it  began  to  boil  when  first  distilled.  Collect  in  the 
proper  flask,  and  continue  the  boiling  until  the  thermometer 
marks  the  highest  point  of  the  fraction  last  introduced,  changing 
the  receiver  whenever  the  indications  of  the  thermometer  require 
it.  Now  stop  the  boiling,  and  pour  in  fraction  No.  3,  and  so 
on  until  all  the  fractions  have  been  subjected  to  a  second  distil- 
lation. On  examining  the  new  fractions,  it  will  be  found  that 
the  liquid  tends  to  accumulate  in  the  neighborhood  of  certain 
points  corresponding  to  the  boiling-points  of  the  constituents  of 
the  mixture.  The  distilling  flask  is  now  cleaned,  and  the  whole 
process  repeated.  A  further  separation  is  thus  effected.  By 
continuing  the  distillation  in  this  way,  pure  substances  may,  in 
most  cases,  eventually  be  obtained.  That  the  fractions  are 
pure  may  be  known  by  the  fact  that  the  boiling-points  remain 
constant.  In  some  cases  perfect  separation  cannot  be  effected 
by  means  of  fractional  distillation  ;  as,  for  example,  in  the 
case  of  alcohol  and  water.  But  still  it  is  valuable,  even  in 
such  cases,  as  it  enables  us  to  purify  the  substances,  at  least 
partially. 

The  best  examples  of  distillation  carried  on  on  the  large  scale 
are  those  of  alcohol  and  petroleum.  Probably  the  best  example 
of  fractional  distillation  is  that  of  the  light  oil  obtained  from 
coal  tar. 


8  INTRODUCTION. 

Experiment  1.  Mix  equal  parts  (about  half  a  litre  of  each)  of  alco- 
hol and  water.  Distil  through  four  or  five  times,  and  notice  the 
changes  in  the  quantities  obtained  in  the  different  fractions. 

Determination  of  the  boiling-point.  —  In  dealing  with 
liquids,  it  often  is  extremely  difficult  to  tell  whether  they  are 
pure  or  not.  The  first  and  most  important  physical  property 
which  is  utilized  for  this  purpose  is  the  boiling  temperature, 
commonly  called  the  boiling-point.  This  is  determined  by 
means  of  an  apparatus,  such  as  is  described  above  as  used  for 
distilling.  The  temperature  noted  on  the  thermometer  when 
the  liquid  is  boiling  is  the  boiling-point.  When  great  accuracy 
is  required,  the  point  observed  directly  must  be  corrected,  in 
consequence  of  the  expansion  of  the  glass  and  the  cooling  of 
that  part  of  the  column  of  mercur}r  which  is  not  in  the  vapor. 
Full  directions  for  making  these  corrections  may  be  found  in 
larger  books.  A  constant  boiling-point  is  characteristic  of  a 
pure  chemical  compound. 

Determination  of  the  melting-point.  —  Just  as  the  boil- 
ing-point is  a  very  characteristic  property  of  liquid  bodies,  so 
the  melting-point  is  an  equally  characteristic  property  of  many 
solid  bodies.  If  a  substance  begins  to  melt  at  a  certain  tem- 
perature, and  does  not  melt  completely  at  that  temperature,  it 
is,  in  all  probability,  impure.  By  means  of  the  melting-point 
minute  quantities  of  impurities,  which  might  readily  escape 
detection  b}>-  other  means,  are  often  found.  In  dealing  with  the 
compounds  of  carbon,  determinations  of  melting-points  are  very 
frequently  made.  In  general,  only  those  compounds  which  have 
constant  melting- points  are  to  be  regarded  as  pure.  The  deter- 
mination is  made  as  follows :  Small  tubes  are  prepared  by 
heating  a  piece  of  ordinary  soft  glass  tubing  of  4mm  to  5mm 
diameter,  and  drawing  it  out.  If  the  parts  are  drawn  apart 
about  12cm  to  15cm,  two  small  tubes  may  be  made  from  the 
narrowed  portion  by  melting  together  in  the  middle,  and  then 
filing  off  each  piece  where  it  begins  to  grow  wider  near  the 


DETERMINATION    OF   THE   MELTING-POINT. 


o 


large  tube.  These  small  tubes  must  have  thin  walls,  and  be 
of  such  internal  diameter  that  an  ordinary  pin  can  be  intro- 
duced into  them.  A  small  quantity  of  the  substance  to  be 
tested  is  placed  in  one  of  the  tubes,  enough  to  make  a  minute 
column  of  about  5mm  in  height.  The  tube  containing  the 
substance  is  fastened  to  a  thermometer  by  means  of  a  small 
rubber  band  cut  from  a  piece  of  rubber  tubing.  The  band  is 
placed  near  the  upper  part  of  the  tube,  and  the  lower  part  of 
the  tube,  containing  the  substance,  is  placed  against  the  bulb 
of  the  thermometer.  Now  a  beaker  glass  of  about  100CC 
capacity  is  filled  with  pure  paraffin,  and  the  latter  melted. 
When  it  is  in  liquid  condition,  the  thermometer,  with  the  tube 
and  substance,  is  introduced 
into  it,  and  the  heating  con- 
tinued with  the  aid  of  a 
small  flame  until  the  sub- 
stance melts.  The  instant  it 
melts  the  temperature  indi- 
cated by  the  thermometer 
is  noted.  This  is  the  melt- 
ing-point required.  It  is 
necessary,  however,  to  cor- 
rect the  observed  point  in 
the  same  way  as  in  the  case 
of  the  boiling-point.  Some- 
times, instead  of  paraffin.  L 

concentrated  sulphuric  acid 
is  used  in  the  bath  ;  but,  for 
obvious  reasons,  the  paraf- 
fin is  to  be  preferred.     For  ^ 
substances  which  melt  below 

80°,    the   temperature    at   which    ordinary    paraffin    is   liquid, 
water  should  be  used. 

Experiment  2.  Determine  the  melting-points  of  a  few  substances, 
such  as  urea  and  tartaric  acid.  If  they  do  not  melt  at  definite  points, 
recrystallize  them  until  they  do.  Note  the  melting-points  observed. 


30  INTRODUCTION. 

and  see  how  well  they  agree  with  those  stated  in  the  book.  The 
arrangement  of  the  apparatus  above  described  is  shown  in  Fig.  3.  To 
secure  a  uniform  temperature  of  the  bath,  it  should  be  gently  stirred 
with  a  glass  rod  during  the  experiment.  The  mercury  of  the  ther- 
mometer should  rise  slowly. 

Analysis.  —  Having  purified  the  compounds,  the  next  step 
Is  to  determine  their  composition.  A  comparatively  small  num- 
ber of  the  compounds  ordinarily  met  with  consist  of  carbon  and 
hydrogen  only  ;  the  largest  number  consist  of  these  two  elements 
together  with  oxygen  ;  many  contain  carbon,  hydrogen,  oxygen, 
and  nitrogen.  But,  in  the  derivatives  of  the  fundamental  com- 
pounds, all  other  elements  may  occur.  Thus  the  hydrogen  may 
be  partly  or  wholly  displaced  by  chlorine,  bromine,  or  iodine,  as 
in  the  so-called  substitution-products  ;  and  any  metal  may  occur 
in  the  salts  of  the  acids  of  carbon.  The  estimation  of  carbon 
and  hydrogen  is  the  principal  problem  in  the  analysis  of  the 
compounds  of  carbon.  This  is  effected  by  what  is  known  as 
the  combustion  process.  A  known  weight  of  the  substance  is 
completely  oxidized,  the  carbon  being  thus  converted  into  car- 
bon dioxide,  and  the  hydrogen  into  water.  These  two  products 
are  collected,  the  carbon  dioxide  in  a  solution  of  potassium 
hydroxide,  the  water  in  calcium  chloride,  and  weighed.  From 
the  weights  of  the  products  the  weights  of  carbon  and  hydrogen 
are  calculated.  Oxygen,  if  present,  is  not  estimated  directly, 
but  by  difference,  *.e.,  the  amounts  of  carbon  and  hydrogen  found 
are  added  together,  and  the  sum  subtracted  from  the  weight  of 
the  original  substance.  The  difference  represents  the  weight 
of  the  oxygen. 

A  detailed  description  of  the  apparatus  and  of  the  method  of 
procedure  need  not  be  given  here,  as  it  can  be  found  in  any 
book  on  analytical  chemistry.  A  brief  description,  however, 
may  not  be  out  of  place.  The  combustion  is  effected  in  a  hard 
glass  tube  which  is  heated  by  means  of  a  gas  furnace  con- 
structed for  the  purpose.  Ordinarily,  the  substance  is  placed 
in  a  narrow  porcelain  or  platinum  vessel,  called  a  boat,  which  is 
introduced  'Mto  the  tube  with  granulated  copper  oxide.  The 


ANALYSIS.  11 

tube  is  then  connected  with  (1)  a  u-tube  filled  with  calcium 
chloride  ;  (2)  a  set  of  bulbs  containing  a  solution  of  potassium 
hydroxide,  and  constructed  so  as  to  secure  thorough  contact  of 
the  passing  gases  with  the  solution ;  and  (3)  a  small  U-tube 
filled  with  solid  potassium  hydroxide.  After  the  combustion  is 
completed,  a  current  of  pure  dry  oxygen  is  passed  through  the 
tube  ;  and,  finally,  air  is  passed  until  the  oxygen  is  displaced. 
The  method  at  present  used  was  introduced  by  Liebig.  It 
has  contributed  very  greatly  to  a  thorough  understanding  of 
the  compounds  of  carbon. 

Two  methods  are  in  common  use  for  the  estimation  of  nitrogen 
in  carbon  compounds.  The  first  is  known  as  the  absolute  method. 
This  consists  in  oxidizing  the  substance  by  means  of  copper 
oxide  ;  then  decomposing,  by  means  of  highly-heated  metallic 
copper,  any  oxides  of  nitrogen  which  may  have  been  formed, 
and  collecting  the  nitrogen.  The  volume  of  the  nitrogen  thus 
obtained  is  measured,  and  its  weight  easily  calculated.  The 
chief  difficulty  in  this  method  consists  in  removing  the  gases 
contained  in  the  apparatus  before  the  combustion  is  made.  To 
do  this,  the  simplest  way  is  to  use  a  mercury  air-pump.  Several 
simple  forms  of  the  pump  have  been  devised  for  this  purpose, 
and  some  of  them  work  admirably.  Having  exhausted  all  the 
air,  the  combustion  is  made  by  heating  the  tube  containing  the 
substance  and  copper  oxide  and  a  layer  of  copper  foil ;  and, 
finally,  the  gases  are  exhausted  at  the  end  of  the  operation. 
The  only  three  gases  which  can  be  present,  assuming  that  the 
substance  contained  nothing  but  carbon,  hydrogen,  oxygen,  and 
nitrogen,  are  carbon  dioxide,  water  vapor,  and  free  nitrogen. 
The  water  vapor  is,  of  course,  condensed,  and  the  carbon  dioxide 
is  absorbed  by  passing  the  gases  through  a  solution  of  potassium 
hydroxide,  leaving  the  nitrogen  thus  alone. 

The  second  method  for  the  estimation  of  nitrogen  consists  in 
heating  the  substance  with  a  mixture  of  sodium  hydroxide  and 
quicklime,  called  soda-lime.  The  nitrogen  is  thus  converted 
into  ammonia,  which  is  collected  in  a  known  quantit}*  of  dilute 


12  INTRODUCTION. 

hydrochloric  or  sulphuric  acid.  After  the  operation,  the  amount 
of  acid  remaining  unneutralized  is  determined  by  titration  ;  and 
from  this  the  amount  of  ammonia  formed  can  be  calculated  ; 
and  from  this,  in  turn,  the  amount  of  nitrogen.  This  method 
is  not  applicable  to  all  compounds,  because  the  nitrogen  of  some 
compounds  is  not  converted  into  ammonia  under  the  circum- 
stances mentioned. 

As  regards  the  estimation  of  other  constituents  of  carbon 
compounds,  it  need  only  be  said  that  in  most  cases  it  is  neces- 
sary to  get  rid  of  the  carbon  and  hydrogen  by  some  oxidizing 
process  before  the  estimation  can  be  made.  Thus,  in  estimating 
sulphur,  it  is  common  to  fuse  the  substance  with  potassium 
nitrate  and  hydroxide,  when  the  carbon  and  hydrogen  are 
oxidized,  and  the  sulphur  is  left  in  the  form  of  potassium  sul- 
phate, and  may  be  estimated  in  the  usual  way. 

Formula.  —  The  deduction  of  the  formula  of  a  compound 
from  the  results  of  the  analysis  involves  two  steps.  The  first 
is  a  matter  of  simple  calculation.  It  is  assumed  that  the 
students  who  use  this  book  are  already  familiar  with  the  method 
of  calculating  the  formula  from  the  analytical  results ;  but  an 
example  will,  nevertheless,  be  given.  Suppose  that  the  analysis 
has  shown  that  the  substance  contains  52.18  per  cent  carbon, 
13.04  per  cent  hydrogen,  and  34.78  per  cent  oxygen.  To  get 
the  atomic  proportions,  divide  the  figures  representing  the  per- 
centages of  the  elements  by  the  corresponding  atomic  weights. 
We  have  thus  :  — 

Per  Af  ,-rr.  Proportionate 

Centage.        At"  wt"  No.  of  Atoms. 

C  52.18  -f-  12  =  4.35  -  2 
H  13.04  -*-  1  =  13.04  -  6 
O  34.78  -r-  16  =  2.17  -  1 

That  is  to  say,  accepting  the  atomic  weights,  12  for  carbon  and 
16  for  oxygen,  the  simplest  figures  representing  the  number  of 
atoms  of  the  three  elements  in  the  compound  are  2  for  carbon, 


FORMULA.  13 

G  for  hydrogen,  and  1  for  oxygen.  According  to  this,  the 
simplest  formula  which  can  be  assigned  to  a  substance  giving 
the  above  results  on  analysis  is  C2HGO.  But  the  formula 
C4H12O2  is  equally  in  accordance  with  the  analytical  results,  and 
we  can  only  decide  between  the  two  by  determining  the  molecular 
weight.  This,  as  is  known,  is  done  by  determining  the  specific 
gravity  of  the  substance  in  the  form  of  vapor.  This  operation 
is  of  the  greatest  importance.  It  is  assumed  that  the  student, 
who  has  already  studied  the  elements  of  inorganic  chemistry,  is 
familiar  with  it,  and  with  the  exact  connection  which  exists 
between  it  and  the  molecular  weights  of  compounds.  A  few 
statements  in  regard  to  the  connection  will,  however,  be  made 
here,  in  order  to  recall  its  chief  points,  and  to  impress  upon  the 
mind  of  the  student  its  fundamental  importance. 

Every  chemical  formula  is  intended  to  represent  the  molecule 
of  a  compound  and  the  composition  of  the  molecule.  Our 
conception  of  the  molecule  is  based  almost  exclusively  on 
Avogadro's  hypothesis,  according  to  which  equal  volumes  of  all 
gases  contain  the  same  number  of  molecules.  Hence,  by  com- 
paring equal  volumes  of  bodies  in  the  form  of  gas  or  vapor,  we 
get  figures  which  bear  to  each  other  the  same  relations  as  the 
weights  of  the  molecules.  The  figures  called  the  specific  gravi- 
ties express  the  relations  between  the  weights  of  equal  volumes. 
In  the  case  of  gases,  air  is  taken  as  the  standard,  and  the 
weights  of  other  gases  are  compared  with  this  standard.  Thus,  if 
we  say  that  the  specific  gravity  of  a  gas  is  0.918,  we  mean  that 
if  we  call  the  weight  of  any  volume  of  air  1,  that  of  the  same 
volume  of  the  other  gas  measured  under  the  same  conditions  of 
temperature  and  pressure  is  0.918.  If  we  assign  to  any  com- 
pound a  certain  molecular  weight,  the  molecular  weights  of  other 
gaseous  compounds  can  be  determined  without  difficulty.  We 
must,  therefore,  first  select  some  substance,  the  molecule  of 
which  may  be  used  as  the  standard.  Hydrochloric  acid  is 
commonly  taken,  because  hydrogen  and  chlorine  unite  with 
each  other  in  only  one  proportion,  and  there  is  good  evidence 


14  INTRODUCTION. 

in  favor  of  the  view  that  it  represents  the  simplest  kind  of 
combination,  viz.,  that  of  one  atom  of  one  element  with  one  of 
another.  Hydrogen  and  chlorine  are  present  in  the  compound 
in  the  proportion  of  1  part  of  hydrogen  to  35.4  parts  of  chlorine  ; 
hence  the  simplest  molecular  weight  which  can  be  assigned  to 
the  compound,  the  atomic  weight  of  hydrogen  being  1,  is  36.4. 
The  molecular  'weight  of  this  standard  molecule  is,  therefore, 
taken  to  be  36.4,  and  we  have  now  simply  to  compare  the 
weights  of  other  gases  with  that  of  hydrochloric  acid  in  order 
to  know  their  molecular  weights.  Thus,  to  illustrate  by  means 
of  the  body  whose  atomic  relations  we  found  by  analysis  to  be 
represented  by  the  formulas  C2H6O,  C4H12O2,  etc.,  if  this  body 
be  converted  into  vapor  and  its  specific  gravity  determined,  it 
might  be  found  to  be  1.6.  The  relation  between  the  molecular 
weight  of  any  body  and  its  specific  gravity  is  expressed  by  the 
equation 

M  =  d  x  28.88, 

in  which  M  is  the  molecular  weight,  and  d  the  specific  gravity 
of  the  substance  in  the  form  of  gas  or  vapor.  As  d  is  1.6  in 
the  case  under  consideration,  we  have 

M  (the  unknown  molecular  weight)  =  1.6  X  28.88  =  46.2. 

If  the  formula  of  the  compound  is  C2HCO,  the  molecular  weight, 
being  the  sum  of  the  weights  of  the  constituent  atoms,  is 

2  X  12  +  6  x  1  +  16  =  46, 

which  agrees  with  the  figure  deduced  from  the  specific  gravity. 
It  therefore  follows  that  the  formula  C2H6O  is  correct. 

There  are  some  other  methods  which  may  be  used  in  deter- 
mining the  molecular  weight  of  a  compound.  Among  these 
may  be  mentioned  the  analysis  of  salts.  To  illustrate  this, 
take  the  case  of  acetic  acid.  Analysis  shows  us  that  it  must  be 
represented  by  one  of  the  formulas  CH2O,  C2H4O2,  C3HCO2,  etc. 
If  we  make  the  silver  salt,  we  find  that  its  analysis  leads  us  to 
the  formula  C2H3O2Ag,  and  not  CHOAg,  and  we  hence  conclude 
that  the  molecular  formula  of  acetic  acid  is  C2H4O2. 


' 

STRUCTURAL  FORMULA.  15 

The  methods  for  determining  the  specific  gravit}'  of  vapors 
are  assumed  to  have  been  described  in  the  course  in  inorganic 
chemistry,  which  the  student  should  have  followed  before  begin- 
ning the  stud}*  of  the  compounds  of  carbon. 

Structural  formula. — The  formulas  C2H6O,  C2H4O2,  C3H8, 

etc.,  tell  us  simply  the  composition  of  the  three  bodies  repre- 
sented, and  tell  us  also  the  relative  weights  of  their  molecules. 
In  studying  the  chemical  conduct  of  these  bodies,  their  decom- 
position, and  the  modes  of  preparing  them,  we  become  familiar 
with  many  facts  which  it  is  desirable  to  represent  by  means  of 
the  formulas.  Thus,  for  example,  but  one  of  the  four  parts  of 
hydrogen  represented  in  the  formula  of  acetic  acid,  C2H4O2,  can 
be  replaced  b}*  metals.  It  plainly  differs  from  the  three  remain- 
ing parts,  and  it  is  natural  to  conclude  that  it  is  held  in  the 
molecule  in  some  way  different!}'  from  the  other  three.  We  may, 
therefore,  write  the  formula  C2H3O2.H,  which  is  intended  to  call 
attention  to  the  difference.  By  further  study  of  acetic  acid,  we 
find  that  that  particular  hydrogen,  which  gives  to  it  its  acid 
properties,  and  which,  in  the  above  formula,  is  written  by  itself, 
is  intimately  associated  with  oxygen.  It  may  be  removed  with 
oxygen  by  very  simple  reactions,  and  the  place  of  both  taken 
by  one  atom  of  some  other  element ;  as,  for  example,  chlorine. 
Thus,  when  acetic  acid  is  treated  with  phosphorus  trichloride^ 
PC13,  it  is  converted  into  acetyl  chloride,  C2H3OC1,  according  to 
this  equation :  — 

3  C2H402  +  PC13  =  3  C2H3OC1  +  K>3H3. 

The  result  of  the  action  is  the  direct  replacement  of  one  atom 
of  hydrogen  and  one  atom  of  oxygen  in  acetic  acid  by  one  atom 
of  chlorine,  a  fact  which  certainly  points  to  an  intimate  connec- 
tion between  the  hydrogen  and  ox}*gen  in  the  acid.  Further, 
when  acetyl  chloride  is  brought  in  contact  with  water,  acetic 
acid  is  regenerated,  hydrogen  and  oxygen  from  the  water  enter- 
ing into  the  place  occupied  by  the  chlorine,  as  represented  iu 
this  equation :  — 

C2H3OC1  +  H2O  =  C2H4O2  +  HC1. 


16  INTRODUCTION. 

From  facts  of  this  kind  the  conclusion  is  drawn  that  in  acetic 
acid  hydrogen  and  oxygen  are  connected;  or,  as  it  is  said,  linked 
together;  and  this  conclusion  is  represented  in  chemical  lan- 
guage by  the  formula  C2H3O.OH,  which  may  serve  as  a  simple 
illustration  of  what  are  called  structured  or  constitutional  for- 
mulas. In  all  compounds  the  attempt  is  made,  by  means  of  a 
thorough  study  of  their  chemical  conduct,  to  trace  out  the 
connections  existing  between  the  constituent  atoms.  When 
this  can  be  done  for  all  the  atoms  contained  in  a  molecule,  the 
structure  or  constitution  of  the  molecule  or  of  the  compound  is 
said  to  be  determined.  The  structural  formulas  which  have 
been  determined  by  proper  methods  have  proved  of  much  value 
in  dealing  with  chemical  reactions,  as  they  enable  the  chemist 
who  understands  the  language  in  which  they  are  written  to  see 
relations  which  might  easily  escape  his  attention  without  their 
aid.  In  order  to  understand  them,  however,  the  student  must 
have  a  knowledge  of  the  reactions  upon  which  the}7  are  based  ; 
and  he  is  warned  not  to  accept  any  chemical  formula  unless  he 
can  see  the  reasons  for  accepting  it.  He  should  accustom  him- 
self to  ask  the  question,  upon  what  facts  is  it  based?  whenever 
a  formula  is  presented  for  the  first  time.  If  he  does  this  con- 
scientiously'  he  will  soon  be  able  to  use  the  language  intelli- 
gently, and  the  beauty  of  the  relations  which  exist  between  the 
large  number  of  compounds  of  carbon  will  be  revealed  to  him. 
If  he  does  not,  his  mind  will  soon  be  in  a  hopeless  muddle, 
and  what  he  learns  will  be  of  little  value  to  him.  For  the 
beginner,  this  piece  of  advice  is  of  vital  importance  :  Study 
with  great  care  the  reactions  of  compounds;  study  the  methods  of 
malting  them,  and  the  decompositions  which  they  undergo.  The 
formulas  are  but  the  condensed  expressions  of  the  conclusions 
which  are  drawn  from  the  reactions. 

General  principle  of  classification  of  the  compounds 
of  carbon.  —  In  considering  the  elements  and  compounds  in- 
cluded under  the  head  of  Inorganic  Chemistry,  the  fundamental 


CLASSIFICATION   OF   COMPOUNDS    OF    CARBON.          17 

substances  are,  of  course,  the  elements.  The  properties  of  the 
elements  enable  us  to  separate  them,  for  study,  into  a  numbei 
of  groups ;  as,  for  example,  the  chlorine  group,  including 
bromine,  iodine,  and  fluorine ;  the  oxygen  group,  in  which 
are  included  sulphur,  selenium,  and  tellurium.  To  recall  the 
method  generally  adopted,  we  may  take  the  chlorine  group. 
In  studying  the  members  of  this  group,  there  is  found  great 
similarity  in  their  properties.  Their  hydrogen  compounds  next 
present  themselves,  and  here  the  same  similarity  is  met  with. 
Then,  in  turn,  the  oxygen  and  the  oxygen  and  hydrogen  com- 
pounds are  considered,  and  again  the  resemblances  in  properties 
between  the  corresponding  compounds  of  chlorine,  bromine,  and 
iodine  are  met  with.  We  thus  have  groups  of  elements,  and 
of  the  derivatives  of  these  elements  :  as,  — 

Cl  C1H  C1O3H 

Br  BrH  BrO3H 

I  IH  IO3H,  etc. 

Of  course,  the  chlorine  group  is  quite  distinct  from  the  oxygen 
group  and  from  all  other  groups  ;  and  each  member  of  the 
chlorine  group  is,  at  least  so  far  as  we  know,  quite  independent 
of  the  other  members.  We  cannot  make  a  bromine  compound 
from  a  chlorine  compound,  or  a  chlorine  compound  from  a 
bromine  compound  without  directly  replacing  the  one  element 
by  the  other. 

Now,  when  we  come  to  study  the  compounds  of  carbon,  we 
shall  find  that  the  same  general  principle  of  classification  is 
made  use  of ;  only,  in  consequence  of  the  peculiarities  of  the 
compounds,  the  system  can  be  carried  out  much  more  perfectly  ; 
the  members  of  the  same  group  can  be  transformed  one  into 
the  other,  and  it  is  also  in  our  power  to  pass  from  one  group  to 
another  by  means  of  comparatively  simple  reactions. 

The  simplest  compounds  of  carbon  are  those  which  contain 
only  hydrogen  and  carbon,  or  the  hydrocarbons.  All  the  other 
compounds  may  be  regarded  as  derivatives  of  the  hydrocarbons. 


18  INTRODUCTION. 

To  begin  with,  there  are  several  groups  or  series  of  hydrocar- 
bons, which  correspond  somewhat  to  the  different  groups  of 
elements.  The  members  of  one  and  the  same  series  of  hydro- 
carbons resemble  each  other  more  closely  than  the  members  of 
one  and  the  same  series  of  elements.  Although  we  have  indica- 
tions of  the  existence  of  more  than  ten  series  of  these  hydrocar- 
bons, only  three  or  four  of  the  series  are  at  all  well  known,  and 
of  these,  but  two  include  more  than  two  or  three  members  which 
will  need  to  be  considered  in  this  book. 

Starting  with  any  series  of  hydrocarbons,  several  classes  of 
derivatives  may  be  obtained  by  treating  the  fundamental  com- 
pounds with  different  reagents.  The  chief  classes  of  these 
derivatives  are  :  (1)  those  containing  halogens  ;  (2)  those  con- 
taining oxygen,  among  which  are  the  acids,  alcohols,  ethers,  etc. ; 
(3)  those  containing  sulphur ;  and  (4)  those  containing  nitro- 
gen. Corresponding  to  every  hydrocarbon,  then,  we  may  expect 
to  find  representatives  of  these  different  classes  of  derivatives. 
But  the  relations  existing  between  any  hydrocarbon  and  its 
derivatives  are  the  same  as  those  existing  between  any  other 
hydrocarbon  and  its  derivatives.  Hence,  if  we  know  what 
derivatives  one  hydrocarbon  can  yield,  we  know  what  deriva- 
tives we  may  expect  to  find  in  the  case  of  every  other  hydro- 
carbon. The  student  who,  for  the  first  time,  undertakes  the 
study  of  carbon  chemistry,  is  very  apt  to  feel  overwhelmed  by 
the  enormous  number  of  compounds  described  in  the  book  or  by 
the  lecturer.  This  large  number  is  really  not  a  serious  matter. 
No  one  is  expected  to  become  acquainted  with  every  compound. 
A  great  many  of  these  need  only  be  referred  to  for  the  purpose 
of  indicating  the  extent  to  which  the  series  to  which  they  belong 
have  been  developed.  In  general,  the  members  of  any  series 
so  closely  resemble  one  another,  that,  if  we  understand  the 
simpler  members,  we  have  a  fair  knowledge  of  the  more  com- 
plicated members. 

It  is  proposed,  in  this  treatise,  to  consider  only  the  more 
important  compounds  apd  the  more  important  reactions,  the 


CLASSIFICATION   OF   COMPOUNDS   OF   CARBON.         19 

object  being  rather  to  give  a  clear,  general  notion  of  the  subject, 
than  detailed  information  regarding  particular  compounds. 
Should  the  student  desire  more  specific  information  concerning 
the  properties  of  any  of  the  compounds  mentioned,  he  can 
easily  find  it  in  some  larger  book.  It  will,  however,  hardly 
be  profitable  for  him,  at  the  outset,  to  burden  his  mind  with 
details.  He  may  thereby  sacrifice  the  general  view,  which  it 
is  so  important  that  he  should  gain  as  quickly  as  possible. 

The  plan  which  will  be  followed  is  briefly  this :  Of  the  first 
series  of  hydrocarbons  two  members  will  be  considered.  Then 
the  derivatives  of  these  two  will  be  taken  up.  These  deriva- 
tives will  serve  admirabl}'  as  representatives  of  the  correspond- 
ing derivatives  of  other  hydrocarbons  of  the  same  series,  and  of 
other  series.  Their  characteristics,  and  their  relations  to  the 
hydrocarbons  will  be  dwelt  upon,  as  well  as  their  relations  to 
each  other.  Thus,  by  a  comparatively  close  study  of  two  hydro- 
carbons and  their  derivatives,  we  may  acquire  a  knowledge  of 
the  principal  classes  of  the  compounds  of  carbon.  After  these 
t}'pical  derivatives  have  been  considered,  the  entire  series  of 
hydrocarbons  will  be  taken  up  briefly,  only  such  facts  being 
dealt  with  at  all  fully  as  are  not  illustrated  by  the  first  two 
members. 

After  the  first  series  has  been  studied  in  this  way,  and  a  clear 
idea  of  the  relations  between  the  various  classes  has  been 
obtained,  a  second  series  will  be  taken  up  anS^reated  in  a 
similar  way,  and  so  on.  But,  as  already  stated,  but  few  of 
the  series  require  very  much  attention  at  the  beginning.  The 
first  series  which  will  be  used  for  the  purpose  of  illustrating  the 
general  principles  is  one  of  the  two  most  important  series,  and 
of  the  only  two  that  need  be  considered  at  all  fully  at  present. 


CHAPTER   II. 

METHANE  AND  ETHANE. -HOMOLOGOUS 
SERIES. 

IF  we  were  to  study  all  the  hydrocarbons  known,  and  were 
then  to  arrange  them  in  groups  according  to  their  properties, 
we  would  find  that  a  large  number  of  them  resemble  marsh  gas 
in  their  general  conduct.  Some  of  the  points  of  resemblance 
.are  these:  They  are  very  stable,  resisting  with  marked  power 
the  action  of  most  reagents  ;  and  nothing  can  be  added  to  them 
directly,  —  if  any  change  takes  place  in  them,  hydrogen  is  first 
given  up.  On  arranging  these  substances  according  to  the 
number  of  carbon  atoms  contained  in  them,  we  have  a  remark- 
able series,  the  first  six  members  of  which,  together  with  their 
formulas,  are  included  in  the  subjoined  table  :  — 

Methane  (or  Marsh  Gas) CH4. 

Ethane C2H6. 

Propane C3H8. 

Butane       .     .     .     .    ^ C4H10. 

Pentane C5H12. 

Hexane C6H14. 

On  examining  the  formulas  given,  we  see  that  the  difference  in 
composition  between  any  two  consecutive  members  is  represented 
by  CH2.  Thus,  adding  CH2  to  marsh  gas,  CH4,  we  get  ethane, 
C2H6 ;  adding  CH2  to  C2H6,  we  get  C3H8,  and  so  on,  in  each 
successive  step.  Any  series  of  this  kind,  in  which  the  succes- 
sive members  increase  in  complexity  by  CH2,  is  called  a  homol- 
ogous series. 

Just  as  the  members  of  a  homologous  series  of  hydrocarbons 


METHANE   AND   ETHANE.  21 

differ  from  one  another  by  CH2,  or  some  multiple  of  it,  so 
also  the  members  of  any  class  of  derivatives  of  these  hydro- 
carbons differ  from  each  other  in  the  same  way,  and  form 
homologous  series.  Thus,  running  parallel  to  the  hydrocarbons 
mentioned  above,  we  have  two  homologous  series  of  oxygen 
derivatives,  as  indicated  below  :  — 

CH4  -CH4O  -  CH2O2- 
C2H6  -  C2H60  -  C2H402. 
C3H8  -  C3H80  -  C3H602. 
C^Hio  —  C4H10O  —  C4H8O2. 
C5H12  -  C5H120  -  C5H1002. 
C6H14  -  C6H140  -  C6H1202. 

The  relation  observed  between  the  members  of  the  homologous 
series  mentioned  is  by  no  means  a  peculiarity  of  the  marsh  gas 
series  of  hydrocarbons  and  of  their  derivatives,  but  is  observed 
in  connection  with  all  other  series  of  hydrocarbons  and  their 
derivatives. 

Strictly  speaking,  there  is  perhaps  no  analogy  for  this  re- 
markable fact  among  the  elements  and  their  compounds,  yet 
facts  which  suggest  analogy  are  known.  Consider,  for  example, 
the  chlorine  series.  We  have 

Chlorine,  with  the  atomic  weight,  35.4 
Bromine,        "  "  "        80. 

Iodine,  "  "  "      127. 

As  is  well  known,  the  difference  between  the  atomic  weights  of 
chlorine  and  bromine  is  approximately  equal  to  the  difference 
between  those  of  bromine  and  iodine.  In  other  words,  there  is 
a  regular  increase  in  complexity  as  we  pass  from  chlorine  to 
iodine.  Or,  at  least,  there  is  a  regular  increase  in  the  atomic 
weights  of  these  similar  elements,  just  as  there  is  a  regular 
increase  in  the  molecular  weights  of  the  similar  members  of  a 
homologous  series.  While,  however,  a  satisfactory  hypothesis 


22  METHANE   AND   ETHANE. 

has  been  offered  to  account  for  the  latter  fact,  and  experi- 
mental evidence  is  strongly  in* favor  of  the  hypothesis,  no  satis- 
factory explanation  of  the  former  has  been  offered ;  or  rather 
no  satisfactory  experimental*  evidence  has  been  furnished  in 
favor  of  the  various  hypotheses  which  from  time  to  time  have 
been  put  forward  to  account  for  the  similarity  between  members 
of  the  same  group  of  elements. 

The  view  at  present  held  in  regard  to  the  nature  of  homology 
is  founded,  primarily,  upon  the  idea  that  carbon  is  quadrivalent. 
If  carbon  is  quadrivalent,  it  will  readily  be  seen  that  the  com- 
pound, marsh  gas,  CH4,  is  saturated ;  that  is,  the  molecule 
cannot  take  up  anything  without  losing  hydrogen.  In  order, 
therefore,  that  we  may  get  a  compound  containing  two  atoms 
of  carbon  in  the  molecule,  some  of  the  hydrogen  must  first  be 
given  up.  With  our  present  views,  we  cannot  conceive  of  union 
taking  place  directly  between  the  molecules  CH4  and  CH4,  but 
we  can  conceive  of  union  taking  place  between  the  molecules 
CH3  and  CH3,  to  form  a  molecule  C2H6,  which  in  turn  is  satu- 
rated. Representing  graphically  what  is  believed  to  take 
place,  we  have,  first,  marsh  gasr  which  we  may  represent  thus, 

H 

I 
H  —  C  —  H.     If  this  loses  one  atom  of  hydrogen,  we  have  the 

I  H 

H  | 

unsaturated  molecule  H  —  C  — ,  which  is  capable  of  uniting  with 

H 
another  molecule  of  the  same  kind  to  form  the  more  complex 

H     H 
I       I 
molecule  H  — C  — C  — H,  or  C2H6,  which  is  believed  to  express 

H     H 

the  relation  existing  between  marsh  gas,  CH4,  and  ethane,  C2H6, 
or  between  any  two  adjoining  members  of  a  homologous  series. 
The  evidence  in  favor  of  this  view  will  be  presented  when  the 
reactions  are  considered  by  means  of  which  the  hydrocar- 
bons are  made.  The  explanation  offered,  and  now  generally 


METHANE    (MARSH   GAS,    FIHE   DAMP).  23 

accepted,  involves  the  idea  that  carbon  atoms  have  the  power 
of  uniting  with  each  other.  And,  as  the  explanation  for  the 
relation  between  the  first  and  second  members  is,  in  principle, 
the  same  as  for  the  relation  between  the  second  and  third,  the 
third  and  fourth,  etc.,  it  appears  that  this  power  of  carbon  atoms 
to  unite  with  each  other  is  very  extensive.  It  is  to  the  power 
which  carbon  possesses  of  forming  homologous  series,  or  to  the 
power  of  the  atoms  of  carbon  to  unite  with  each  other,  that  we 
owe  the  large  number  of  compounds  of  this  element. 

Methane  (marsh  gas,  fire  damp),  CH4.  —  This  hydro- 
carbon is  found  rising  from  pools  of  stagnant  water  in  marshy 
districts.  If  a  bottle  be  filled  with  water  and  inverted  with  a 
funnel  in  its  neck  in  such  a  pool,  some  of  the  gas  may  be  col- 
lected by  holding  the  funnel  over  the  bubbles  rising  from  the 
bottom.  It  is  also  found  in  large  quantities  mixed  with  air,  in 
coal  mines,  and  sometimes  issues  from  the  earth,  in  company 
with  other  gases,  in  the  neighborhood  of  petroleum  wells. 

It  may  be  prepared  by  passing  a  mixture  of  carbon  bisulphide 
and  hydrogen  sulphide  or  water  vapor  over  ignited  metals,  as 
indicated  in  the  following  equations  :  — 

CSa  +  2  H2S  +  8  Cu  =  CH4  +  4  Cu2S, 
and       CS2  +  2  H2O  +  6  Cu  =  CH4  +  2  Cu2S  +  2  CuO. 

•These  methods  are  of  special  interest  for  the  reason  that  they 
indicate  the  possibility  of  making  marsh  gas  from  the  elements  ; 
carbon  bisulphide,  hydrogen  sulphide,  and  water  all  being  made 
readily  from  the  elements. 

It  is  formed,  as  its  occurrence  in  marshes  indicates,  by  the 
decomposition  of  organic  matter  under  water.  In  pure  con- 
dition it  is  made  most  readily  by  mixing  2  parts  sodium  acetate, 
2  parts  potassium  hydroxide,  and  3  parts  quicklime,  and  heat- 
ing the  mixture.  Writing  sodium  instead  of  potassium  hydrox- 
ide, the  action  which  takes  place  is  represented  thus  :  — 

+  NaOH  =  CH4  +  Xa2CO3. 


24  METHANE   AND   ETHANE. 

It  will  be  shown  hereafter  that  most  acids  of  carbon  break  up 
in  a  similar  way,  yielding  a  hydrocarbon  and  a  carbonate. 

Properties.  Marsh  gas  is  colorless  and  inodorous.  It  is 
slightly  soluble  in  water,  but  not  so  much  so  as  to  prevent  its 
collection  over  water.  It  burns.  Its  mixture  with  air  is  explo- 
sive. It  is  this  mixture  which  is  the  cause  of  the  explosions 
which  so  frequently  take  place  in  coal  mines. 

Experiment  3.  Make  marsh  gas  from  sodium  acetate.  Collect 
over  water.  Burn  some  as  it  escapes  from  a  jet.  Mix  a  little  with 
seven  to  eight  times  its  volume  of  air  in  a  wide-mouthed  cylinder  of 
not  more  than  150  to  200CC  capacity.  Explode  by  applying  a  lighted 
taper. 

Reagents,  in  general,  do  not  act  readily  upon  marsh  gas. 
Chlorine  in  diffused  daylight  gradually  replaces  the  hydrogen, 
forming  a  series  of  compounds  which  will  be  considered  under 
the  head  of  the  halogen  derivatives  of  methane.  The  simplest 
of  them  has  the  composition  represented  by  the  formula  CH3C1, 
and  is  known  as  chlor-methane  or  methyl  chloride. 

Ethane,  C2H6.  —  Ethane  rises  from  the  earth  from  some  of 
the  gas  wells  in  the  regions  in  which  petroleum  occurs.  It  is 
also  found  dissolved  in  crude  petroleum. 

It  can  be  made  from  methane  by  introducing  a  halogen  and 
making  a  compound  like  chlor-methane,  CH3C1.  As  the  corre- 
sponding iodine  derivative  is  less  volatile,  it  is  used.  This  iodo- 
methane,  CH3I,  is  treated  with  zinc  or  sodium  in  some  neutral 
medium,  as,  for  example,  anhydrous  ether.  The  reaction  which 
takes  place  is  represented  thus  :  — 

CH3I  +  CH3I  +  2  Na  =  C2H6  +  2  Nal. 

This  method  of  building  up  more  complex  from  simpler  hydro- 
carbons has  been  used  extensively  ;    and  it  is  well  calculated 
to  show  the  relations  between  the  substances  formed  and  the 
simpler  ones  from  which  they  are  made. 
An  operation  of   the  kind  involved  in  the  above-mentioned 


ETHANE.  25 

preparation  of  ethane  is  called  a  synthesis.  The  essential  feature 
of  the  synthesis  is  the  formation  of  a  more  complex  body  from 
simpler  ones.  Our  knowledge  of  the  structure  of  the  compounds 
of  carbon  is  largely  dependent  upon  the  use  of  various  methods 
of  synthesis.  For  example,  in  the  case  under  consideration,  the 
synthesis  gives  us  at  once  a  clear  view  of  the  relations  between 
ethane  and  methane,  and  also  suggests  that  home-logy  may  be 
due  to  similar  relations  between  the  successive  members  of  the 
series,  —  a  view  which  is  fully  confirmed  by  the  synthetical  prep- 
aration of  the  higher  members.  A  similar  method  of  synthesis 
has  been  used  in  the  preparation  of  tetrathionic  acid  from 
sodium  thiosulphate.  The  action  is  represented  thus:  — 


Na2S2O3  1  ,    T  ._  NaS2O8        , 

Na2S  A  >  NaS  A 

Two  mol.  sodium  Sodium  tetra- 

tbiosulphate.  thionate. 


CHAPTER   III. 

HALOGEN    DERIVATIVES    OP   METHANE 
AND    ETHANE. 

Substitution. — When   methane   and    chlorine   are  brought 

O 

together  in  diffused  daylight,  action  takes  place  gradually ; 
hydrochloric  acid  gas  is  given  off,  and  one  or  more  products 
are  obtained,  according  to  the  length  of  time  the  action  con- 
tinues. The  products  have  been  studied  carefully,  and  four 
have  been  isolated.  The  composition  of  these  products  is  repre- 
sented by  the  formulas  CH3C1,  CH2C12,  CHC13,  and  CC14.  We 
see  thus  that  the  action  of  chlorine  consists  in  replacing,  step 
by  step,  the  hydrogen  of  the  hydrocarbon.  The  action  is  repre- 
sented by  the  four  equations  :  — 

(1)  CH4       +  C12  =  CH3C1   +  HC1; 

(2)  CH3C1  +  C12  =  CH2C12  +  HC1 ; 

(3)  CH2C12  +  C12  =  CHC13  +  HC1 ; 

(4)  CHC13   +  C12  =  CC14      +  HC1. 

This  replacement  of  hydrogen  by  chlorine  is  an  example  of 
what  is  known  as  substitution.  We  shall  find  that  most  hydro- 
carbons are  very  susceptible  to  the  influence  of  the  halogens 
and  a  number  of  other  reagents,  such  as  nitric  acid,  sulphuric 
acid,  etc.,  and  that  thus  a  large  number  of  derivatives  may  be 
made,  differing  from  the  hydrocarbons  in  that  they  contain  one 
or  more  halogen  atoms  or  complex  groups  in  the  place  of  the 
same  number  of  l^drogen  atoms.  It  must  be  borne  in  mind 
that  the  mere  fact  that  chlorine,  in  acting  upon  marsh  gas, 
replaces  an  equivalent  quantity  of  hydrogen,  does  not  prove  that 


DI-IODOMETHANE.  27 

the  chlorine  in  the  product  occupies  the  same  place  that  the 
replaced  hydrogen  did.  Nevertheless,  a  careful  study  of  all 
the  facts  regarding  the  products  thus  formed  has  led  to  the 
belief  that  the  substituting  atom  or  residue  does  occupy  the 
same  place,  or  bear  the  same  relation  to  the  carbon  atom  as 
the  hydrogen  did. 

The  name  substitution-products  properly  includes  all  products 
made  from  the  hydrocarbons,  or  from  other  carbon  compounds, 
by  the  substitution  process.  The  principal  ones  are  those 
formed  by  the  action  of  the  halogens,  or  the  halogen  substitution- 
products;  those  formed  by  the  action  of  nitric  acid,  or  the  nitro- 
substitution-products  ;  and  those  formed  by  the  action  of  sulphuric 
acid,  or  the  sulphonic  acids.  The  last  are,  however,  not  com- 
monly  spoken  of  as  substitution-products. 

Chlor-methane,  methyl  chloride,  CH3C1. 

Brom-methane,  methyl  bromide,  CH3Br. 

lodo-methane,     methyl  iodide,      CH3I. 

The  chlorine  and  bromine  products  can  be  made  by  treating 
methane  with  the  corresponding  element.  They  can  be  most 
easily  made  by  treating  methyl  alcohol  with  the  corresponding 
hydrogen  acids  :  — 

CH4O  +  HC1  =  CH3C1  +  H2O. 

Methyl  alcohol.  Chlor-methane. 

Di-iodo-methane,  methylene  iodide,  CH2I2.  —  This  sub- 
stance is  the  principal  halogen  derivative  of  methane  containing 
two  halogen  atoms.  It  is  made  from  iodoform  or  tri-iodo- 
methane,  CHI3,  by  treating  with  hydriodic  acid,  which  latter 
acts  simply  as  a  reducing  agent :  — 

CHI3  +  H2  -  CH2I2  +  IH. 

As  will  be  seen,  this  is  a  case  of  reverse  substitution;  in  other 
words,  the  action  is  the  opposite  of  that  described  above  as 
substitution.  Methylene  iodide  is  a  liquid  which  boils  at  180°, 
and  has  the  specific  gravity  3.342. 


28  DEEIVATIVES   OF   METHANE   AND   ETHANE. 

Chloroform,  CHC13.  -\  The  best  known  and  most  exten- 
Bromoform,  CHB3.  >•  sively  used  of  these  three  derivatives 
lodoform,  CHI3.  3  is  chloroform  or  tri-chlor-methane.  It 
is  made  by  treating  ordinan*  alcohol  with  "  bleaching  powder." 
The  action  is  deep-seated,  involving  at  least  three  different 
stages.  It  will  be  referred  to  more  fully  under  the  head  of 
chloral  (which  see) .  Chloroform  is  a  heavy  liquid  of  specific 
gravity  1.526.  It  has  an  ethereal  odor,  and  a  somewhat  sweet 
taste.  It  is  scarcely  soluble  in  water.  It  boils  at  62°.  It  is 
one  of  the  most  valuable  anaesthetics,  though  there  is  some 
danger  attending  its  use. 

Experiment  4.  Mix  430s  good  bleaching  powder  and  1|  litres  water 
in  a  good  sized  flask.  Add  100CC  alcohol  (88  to  89  per  cent),  and  100s 
quicklime,  and  distil  in  a  water  bath.  A  mixture  of  alcohol,  water, 
and  chloroform  collects  in  the  receiver.  Add  milk  of  lime  and  calcium 
chloride.  Remove  the  chloroform  by  means  of  a  pipette. 

lodoform,  which  is  used  quite  extensively  in  surgery,  is  made 
by  bringing  together  alcohol,  an  alkali,  and  iodine.  It  is  a 
solid  substance,  soluble  in  alcohol  and  ether,  but  insoluble  in 
water.  It  c^stallizes  in  delicate,  six-sided,  yellow  plates. 
Melting-point,  119°. 

Experiment  5.  Dissolve  20s  crystallized  sodium  carbonate  in  100s 
water.  Pour  10s  alcohol  into  the  solution,  and,  after  heating  to  60°  to 
80°,  add  gradually  10&  iodine.  The  iodoform  separates  from  the  solu- 
tion. 

Tetra-chlor-methane,  CC14,  is  made  by  treating  carbon  bisul- 
phide with  chlorine,  and  by  treating  chloroform  with  iodine 
chloride,  IC1. 

Equivalence  of  the  hydrogen  atoms  in  methane.  Having  thus 
seen  that  the  hydrogen  atoms  of  methane  can  easily  be  replaced, 
an  interesting  question  suggests  itself  as  to  whether  these  hydro- 
gen atoms  all  bear  the  same  relation  to  the  carbon  atom.  We 
accept  the  conclusion  that  the  carbon  atom  is  quadrivalent. 


IODOETHANE.  29 

and  that  each  of  the  four  hydrogen  atoms  is  in  combination 


with  it,  as  indicated  in  the  formula  (4)H-C-H(2).     Do  the 

H(3) 

atoms  numbered  1,  2,  3,  and  4  bear  the  same  relation  to  the 
carbon  or  not?  If  they  do  not,  then,  on  replacing  H  (1)  by 
chlorine,  the  product  should  be  different  from  that  obtained  by 
replacing  H  (2),  PI  (3),  or  H  (4)  ;  or,  it  should  be  possible 
to  make  more  than  one  variety  of  chlor-methane  and  of  similar 
products.  This  subject  is  an  extremely  difficult  one  to  deal 
with.  We  can  only  say  that,  although  chlor-methane  has  been 
made  in  several  ways,  the  product  obtained  is  always  the 
same  one  ;  and  the  same  is  true  of  all  other  substitution  -pro- 
ducts of  methane.  Hence,  we,  have  no  reason  whatever  for 
believing  that  there  are  any  differences  between  the  hydrogen 
atoms  of  methane.  We  therefore  conclude  that  they  all  bear  the 
same  relation  to  the  carbon  atom, 

This  conclusion  is  of  fundamental  importance  in  dealing  with 
the  higher  members  of  the  methane  series,  and,  indeed,  in  deal- 
ing with  all  carbon  compounds,  as  will  be  seen  later. 

• 

Chlor-ethane,  ethyl  chloride,  C2H5C1. 

Brom-ethane,   ethyl  bromide,  C2H5Br. 

lodo-ethane,      ethyl  iodide,        C2H5I. 

These  substances  are  all  liquids  having  pleasant  ethereal  odors. 
The  first  boils  at  12°,  the  second  at  38.8°,  and  the  third  at  72°. 
The}'  are  most  readily  made  from  alcohol,  by  treating  with  the 
corresponding  hydrogen  acids.  In  the  case  of  the  bromide  and 
iodide,  it  is  simpler  to  treat  the  alcohol  with  red  phosphorus 
and  the  halogen.  The  action  is  similar  to  that  involved  in 
making  hydrobromic  acid  by  treating  water  with  red  phosphorus 
and  bromine.  It  will  be  shown  that  alcohol  is  a  hydroxide, 
in  which  hydroxyl  (OS)  is  in  combination  with  the  group  C2H5, 
called  ethyl,  as  represented  in  the  formula  C2H5.OH.  When 


30 


DERIVATIVES   OF   METHANE  AND   ETHANE. 


bromine  is  brought  in  contact  with  red  phosphorus,  the  tribro- 
mide,  PBr3,  is  formed,  and  this  acts  upon  the  alcohol  thus  :  — 


C2H5.OH 
Cft.OH  +  Br 
C2H5.OH       Br 


=  3  C2H5Br  +  P(OH)8. 


When  water  is  used  instead  of  alcohol,  the  bromine  appears  in 
combination  with  hydrogen  as  hydrobromic  acid. 

Experiment  6.    Arrange  ail  apparatus  as  represented  in  Fig.  4. 
In  the  flask  place  108  red  phosphorus  and  60s  absolute  alcohol.    Put 
60s  bromine  in  the  glass-stoppered  funnel,  and,  by  means  of  the  stop- 


Fig.  4. 

cock,  let  the  bromine  enter  the  flask  very  slowly,  drop  by  drop.  After 
allowing  the  mixture  to  stand  for  two  or  three  hours,  gently  heat  the 
water-bath,  and  the  brom-ethane  will  distil  over.  Place  the  distillate  in 
a  glass-stoppered  cylinder,  and  shake  it  first  with  water  to  which  some 
caustic  soda  has  been  added,  and  then  two  or  three  times  with  water 
alone.  Separate  the  water  from  the  brom-ethane  either  by  means  of  a 
pipette1  or  a  separating  funnel.  Add  two  or  three  pieces  of  fused 

1  A  good  pipette  for  separating  two  liquids  of  different  specific  gravities  maybe  easily 
made  as  follows:  Select  a  piece  of  glass  tubing  about  1.5  to  2'm  internal  diameter,  and  a 


ISOMERISM.  31 

calcium  chloride  the  size  of  a  small  marble,  and  let  stand  for  a  few 
hours.  Then  pour  off  into  a  clean,  dry  distilling  bulb,  and  distil,  noting 
the  boiling-point. 

Among  the  many  halogen  substitution-products  of  ethane 
containing  more  than  one  halogen  atom,  only  two  will  be  men- 
tioned. These  are  the  two  di-chlor-ethanes,  both  of  which  are 
represented  by  the  formula  C2H4C12.  The  existence  of  these 
two  substances,  having  the  same  composition  but  entirely  differ- 
ent properties,  affords  a  good  example  of  what  is  known  as 
isomerism. 

Isomerism.  —  One  of  the  most  striking  and  interesting  facts 
with  which  we  become  familiar  in  studying  carbon  compounds, 
is  the  frequent  occurrence  of  two,  and  often  more,  substances 
containing  the  same  elements  in  the  same  proportions  by  weight. 
Substances  which  bear  this  relation  to  one  another  are  said  to 
be  isomeric. 

Isomerism  is  of  two  kinds  :  (1)  Substances  may  have  the  same 
per  centage  composition  and  the  same  molecular  weights.  Such 
bodies  are  said  to  be  metameric.  The  di-chlor-ethanes,  C2H4C12, 
for  example,  are  metameric.  (2)  Substances  which  have  the  same 
per  centage  composition  but  different  molecular  weights  are  said 
to  be  polymeric.  Acetylene,  C2H2,  benzene,  C6HC,  and  styrene, 
C8H8,  are  polymeric. 

second  that  will  fit  snugly  into  it,  so  that  it  can  be  moved  up  and  down  without  difficulty. 
Draw  out  the  larger  tube,  and  fit  to  it  a  tube  of  about  6mm  diameter  and  16cm  long. 
Then  draw  out  this  last  tube  to  a  small  opening.  Close  the  smaller  of  the  two  large  tubes 
by  melting  it  together.  Finally,  put  this  tube  into  the  largest  one,  and  draw  over  the  two 
a  broad  piece  of  thick  rubber  tubing,  which  will  close  the  opening  between  the  two,  and 
at  the  same  time  permit  the  upward  and  downward  movement  of  the  smaller  tube.  The 
pipette  has  the  form  represented  in  Fig.  5. 


Fig.  5. 

The  dimensions  may  be  varied,  but  the  following  will  be  found  convenient:  length  of 
widest  tube  about  16  to  20«m;  total  length  of  inner  tube,  or  piston,  about  25  to  30cm.  In- 
stead of  drawing  the  large  tube  out  and  fitting  the  smaller  tube  to  it,  the  union  may  be 
made  by  means  of  a  cork. 


32  DERIVATIVES   OF  METHANE   AND   ETHANE. 

The  cause  of  isomerism  is  undoubtedly  to  be  found  in  the 
different  relations  which  the  parts  of  isomeric  compounds  bear 
to  each  other.  Our  structural  formulas,  which  show  the  relations 
between  the  parts  of  compounds  which  have  been  traced  out  by 
a  study  of  the  chemical  conduct  of  these  compounds,  give  us  an 
insight  into  the  causes  of  isomerism.  To  illustrate,  let  us  take 
the  two  di-chlor-ethanes.  One  of  these  is  made  by  treating 
ethane,  the  other  by  treating  ethylene,  C2H4,  with  chlorine. 
In  the  first  case  the  action  is  substitution  ;  in  the  second,  the 
chlorine  is  added  directly  to  ethylene,  thus,  — 

C2H4  +  C12  =  C2H4C12. 

The  product  from  ethylene  is  called  ethylene  chloride;  that  from 
ethane,  ethylidene  chloride.  It  will  be  shown  that  ethylene  is  to 

CH2 
be  represented  by  the  formula  I      ;  that  is,  that  in  it  two  hydro- 

CH2 

gen  atoms  are  in  combination  with  each  of  the  carbon  atoms. 
Now,  if  chlorine  is  brought  in  contact  with  this  substance,  we 
would  naturally  expect  each  of  the  carbon  atoms  to  take  up  one 
atom  of  chlorine,  and  thus  to  become  saturated,  as  represented 
in  the  equation, — 

CH,       Cl       CH2C1 

I       +       =    I 

CH2       Cl       CH2C1. 

Chlorine  is  taken  up,  and  it  is  believed  that  the  ethylene 
chloride  obtained  has  the  structure  represented  in  the  formula 

CH2C1 

I         ,  the  distinctive  feature  of  which  is  that  each  of  the  chlorine 

CH2C1 

atoms  is  in  combination  with  a  different  carbon  atom. 

We,  however,  can  conceive  of  another  possibility  ;  viz.,  that 
the  chlorine  atoms  are  both  in  combination  with  the  same 

CHC12 

carbon  atom,   as  represented  in  the  .formula    |         ,    and    we 

CH3 

would  be  inclined  to  the  view  that  this  represents  the  structure 


ISOMEBISM.  33 

of  ethylidene  chloride.  Fortunately  we  have  experimental  evi- 
dence to  support  this  view.  It  will  be  shown  that  aldehyde 

CHO 

has  the  formula    |       .     When  aldehyde  is  treated  with  phos- 
CH3 

phorus  pentachloride,  two  chlorine  atoms  take  the  place  of  the 
oxygen.  A  product  which  must  be  represented  by  the  formula 

CHCL, 

I  is  formed,  and  this  is  identical  with  ethylidene  chloride. 

CH3 

Thus  it  will  be  seen  that  the  difference  between  the  two  iso- 
meric  compounds,  ethylene  chloride  and  ethylidene  chloride, 
may  be  said  to  depend  upon  the  fact  that  in  the  former  the 
two  chlorine  atoms  are  in  combination  with  different  carbon 
atoms,  while  in  the  latter  both  are  in  combination  with  the  same 
carbon  atom. 

General  characteristics  of  the  halogen  derivatives  of  methane 
and  ethane.  The  one  characteristic  to  which  it  is  desirable 
that  special  attention  should  be  called  is  the  firmness  with  which 
the  halogens  are  held  in  the  compounds.  Chlorine,  in  combina- 
tion with  a  metal  in  the  form  of  a  soluble  compound,  can  always 
be  removed  by  addition  of  silver  nitrate.  It  cannot  easily  be 
so  removed  when  present  in  substitution  products  of  the  hydro- 
carbons. If  silver  nitrate  be  added  to  a  solution  of  chlor- 
methane,  CH3C1,  no  precipitate  is  formed.  On  the  other  hand, 
when  chlor-me thane  is  heated  with  a  silver  compound,  the  chlorine 
is  removed.  Sodium  and  zinc  have  the  power  of  extracting  the 
chlorine,  bromine,  etc.,  from  halogen  derivatives,  and  this  fact 
is  taken  advantage  of  in  the  synthesis  of  many  hydrocarbons. 
(See  "Ethane,"  p.  24.) 


CHAPTER   IV. 

OXYGEN    DERIVATIVES    OP   METHANE 
AND   ETHANE. 

THERE  are  several  classes  of  oxygen  derivatives  of  the  hydro- 
carbons. Among  them  are  the  important  compounds  known  as 
alcohols,  ethers,  aldehydes,  and  acids.  Each  of  these  classes 
will  be  taken  up  in  turn. 

1.  ALCOHOLS. 

Among  the  most  important  oxygen  derivatives  are  the  alco- 
hols, of  which  methyl  alcohol,  or  wood  spirits,  and  ethyl  alcohol, 
or  spirits  of  wine,  are  the  best  known  examples.  As  far  as 
composition  is  concerned,  these  bodies  bear  very  simple  relations 
to  the  two  hydrocarbons,  methane  and  ethane.  These  rela- 
tions are  indicated  by  the  formulas,  - 

Hydrocarbons.  Alcohols. 

CH4  CH4O 

C2H6  C2H6O. 

The  molecule  of  the  alcohol  differs  from  that  of  the  correspond- 
ing hydrocarbon  by  one  atom  of  oxygen.  In  order  to  under- 
stand the  chemical  nature  of  alcohols,  it  will  be  best  to  study 
with  some  care  the  reactions  of  one  ;  and  we  may  take  for  this 
purpose  the  simplest  one  of  the  series,  viz.,  methyl  alcohol. 

Methyl  alcohol,  CH4O.  —  This  alcohol  is  known  also  as 
wood  spirits.  It  is  found  in  nature  in  combination  in  the  oil 
of  wintergreen.  It  is  formed,  together  with  many  other  sub- 
stances, in  the  dry  distillation  of  wood.  It  is  hence  contained 
in  crude  pyroligneous  acid  or  wood  vinegar.  Wood  is  distilled 
in  large  quantities  for  various  purposes ;  chiefly  however,  for 


METHYL   ALCOHOL.  35 

making  charcoal.  In  some  charcoal  factories  the  distillate  is 
collected  and  utilized.  Wood  is  distilled  also  for  the  purpose 
of  making  vinegar,  or  pure  acetic  acid. 

It  is  not  an  easy  matter  to  get  pure  methyl  alcohol  from  crude 
wood  spirits.  Fractional  distillation  alone  will  not  answer ; 
though,  if  the  mixture  be  distilled  for  some  time,  and  the  impure 
alcohol  thus  obtained  then  converted  into  some  crystalline  deriv- 
ative, the  latter  can  be  purified  and  then  decomposed  in  such 
a  wa}r  as  to  yield  the  alcohol  in  pure  condition. 

Methyl  alcohol  is  a  liquid  which  boils  at  66.7°,  and  has  the 
specific  gravity  0.8142  at  0°.  It  closely  resembles  ordinary 
alcohol  in  all  its  properties.  It  burns  with  a  non-luminous 
flame.  When  taken  into  the  system  it  intoxicates.  In  concen- 
trated form  it  is  poisonous.  It  is  an  excellent  solvent  for  fats, 
oils,  resins,  etc.,  and  is  extensively  used  for  this  purpose. 

1.  Action  of  hydrochloric,  hydrobromic,  and  other  acids  on 
methyl  alcohol.     The  action  of  a  few  acids  is  represented  by 
the  following  equations  :  — 

CH4O  +  HBr  =  CH3Br  +  H2O ; 
CH4O  +  HC1  =  CH3C1  +  H2O ; 
CH4O  +  HNO3  =  CH3NO3_  +  H2O ; 

2  CH4O  +  H2SO4  =  (CH3)2SO4  +  2  H2O. 

The  action  is  plainly  suggestive  of  that  of  metallic  hydroxides 
or  bases.  In  each  case  the  acid  is  neutralized  and  water  is 
formed,  just  as  the  acid  would  be  neutralized  by  potassium 
hydroxide. 

2.  Action  of  phosphorus  trichloride.     When  phosphorus  tri- 
chloride acts  on  methyl  alcohol,  the  products  are  chlor-me thane 
and  phosphorous  acid  :  — 

3  CH4O  +  PC13  =  3  CH3C1  +  P(OH)g. 

Here  an  atom  of  oxygen  and  an  atom  of  hydrogen  are  together 
replaced  by  one  atom  of  chlorine,  the  reaction  being  like  that 
which  takes  place  between  water  and  phosphorus  trichloride  :— - 

3  H2O  +  PC13  =  3  HC1  +  P(OH)3. 


36  DERIVATIVES    OF   METHANE   AND    ETHANE. 

This  fact  would  lead  us  to  suspect  that  there  is  some  resem- 
blance between  the  alcohol  and  water. 

3.  Action  of  potassium  and  sodium.  When  potassium  is 
brought  in  contact  with  pure  methyl  alcohol,  hydrogen  is  given 
off,  and  a  compound  containing  potassium  is  formed :  — 

CH4O  +  K  =  CH3KO  +  H. 

Further  treatment  of  this  compound  with  potassium  causes  no 
further  evolution  of  hydrogen,  so  that  plainly  one  of  the  four 
hydrogen  atoms  contained  in  methyl  alcohol  differs  from  the 
other  three. 

The  resemblance  between  methyl  alcohol  and  metallic  hy- 
droxides ;  the  replacement  of  hydrogen  and  oxygen  by  chlorine  ; 
and  the  resemblance  between  the  alcohol  and  water ;  and, 
finally,  the  replacement  of  one,  and  only  one,  hydrogen  atom 
by  potassium,  lead  to  the  conclusion  that  the  alcohol  contains 
hydrogen  and  oxygen  in  combination,  and  that  the  characteristic 
reactions  are  due  to  the  presence  of  the  group  called  hydroxyl 
(OH) .  The  analogy  between  the  alcohol,  a  metallic  hydroxide, 
and  water,  is  shown  by  these  formulas:  alcohol,  CH3.OH; 
hydroxide,  K.OH  ;  water  H.OH.  Thus  water  appears  as  the 
type  of  both  the  hydroxide  and  the  alcohol,  and  they  may  be 
regarded  as  derived  from  water  by  replacing  one  hydrogen  atom 
by  the  group  CH3,  in  the  case  of  the  alcohol,  and  the  metal 
potassium  in  the  case  of  the  hydroxide.  Or,  on  the  other  hand, 
methyl  alcohol  may  be  regarded  as  marsh  gas  in  which  one  of 
the  hydrogen  atoms  is  replaced  by  hydroxyl.  This  is  the  view 
which  is  universally  held. 

To  test  the  correctness  of  the  view,  we  may  try  to  make 
methyl  alcohol  in  some  way  that  will  show  us  of  what  parts  it  is 
made  up.  Thus,  we  might  start  with  marsh  gas,  and  introduce 
a  halogen,  as  bromine.  Now,  if  we  bring  brom-methaue  to- 
gether with  a  metallic  hydroxide,  the  bromine  and  the  metal 
may  unite,  leaving  the  hydroxyl  and  the  group  CH3,  which  may 
unite  also,  as  indicated  in  the  equation 

CH3Br  +  MOH  =  CH3.OH  +  MBr. 


ETHYL  ALCOHOL.  37 

If  methyl  alcohol  conld  be  made  in  this  way,  we  should  have 
very  clear  proof  of  the  correctness  of  the  view  expressed  in  the 
formula  CH3  .OH.  While  no  reaction  of  this  kind  has  been  used 
in  the  preparation  of  methyl  alcohol,  so  many  alcohols  have  been 
made  in  this  way  that  the  proof  is  overwhelming. 

The  reactions  above  considered  show  that  the  part  of  methyl 
alcohol  which  corresponds  to  the  metal  in  the  hydroxide  is  the 
group  CH3.  This  it  is  which  enters  into  the  acids  in  place  of 
their  hydrogen,  and  this  remains  unchanged  when  potassium 
acts  upon  the  alcohol.  It  has  received  the  name  methyl.  Hence 
we  have  the  names  methyl  alcohol,  methyl  bromide,  methyl 
ether,  etc.  A  group  which,  like  methyl,  appears  in  a  number 
of  compounds  is  called  a  radical,  or  residue.  These  names  are 
intended  simply  to  designate  that  part  of  a  carbon  compound 
which  remains  unchanged  when  the  compound  is  subjected  to 
various  transforming  influences. 

The  two  most  characteristic  reactions  of  methyl  alcohol  are  : 
(1)  its  power  to  form  salt-like,  neutral  bodies  when  treated 
with  acids  ;  and  (2)  its  power  to  form  an  acid  when  oxidized. 

The  neutral  bodies  formed  with  acids  correspond  to  the  salts 
of  metals,  only  they  contain  the  radical,  or  residue,  methyl, 
CH3,  in  the  place  of  metals.  They  are  called  compound  ethers 
or  ethereal  salts. 

The  acid  formed  by  oxidation  has  the  composition  expressed 
by  the  formula  CH2O2.  It  differs  from  the  alcohol  by  contain- 
ing one  atom  of  oxygen  more  and  two  atoms  of  hydrogen  less. 
It  will  be  shown  that  this  acid  is  the  first  of  an  important  series 
of  acids,  known  as  the  fatty  acids,  each  of  which  bears  the  same 
relation  to  a  hydrocarbon  containing  the  same  number  of  carbon 
atoms  that  this  simplest  acid  bears  to  marsh  gas. 

Ethyl  alcohol,  C,H5  .OH.  —  This  is  the  best  known  sub- 
stance belonging  to  the  class  of  alcohols.  It  is  known  also  by 
the  names  spirits  of  wine  and  ordinary  alcohol.  It  occurs  in 
small  quantities  widely  distributed  in  nature. 


38  DERIVATIVES    OF   METHANE   AND   ETHANE. 

The  one  method  of  preparation  upon  which  we  are  dependent 
for  alcohol  is  the  fermentation  of  sugar. 

Fermentation.  —  Whenever  a  plant  juice  which  contains 
sugar  is  left  exposed  to  the  air,  it  gradually  undergoes  a  change 
by  which  it  loses  its  sweet  taste.  Usually  the  change  consists 
in  a  breaking  up  of  the  sugar  into  carbon  dioxide  and  alcohol. 
The  equation 

C6H1206  =  2  C2H60  +  2  C02, 

Sugar.  Alcohol. 

approximately  expresses  what  takes  place  in  the  process  which 
is  known  as  alcoholic  fermentation.  It  has  been  shown  that 
fermentation  is  caused  by  the  presence  of  small  organized 
bodies,  either  animal  or  vegetable.  These  bodies,  which  are 
known  as  ferments,  are  of  different  kinds,  and  cause  different 
kinds  of  fermentation  with  different  products.  Among  the  kinds 
of  fermentation  the  following  may  be  specially  mentioned  :  — 

1.  Alcoholic  or  vinous  fermentation.     This  is  caused   by  a 
vegetable  ferment  which  is  contained  in  ordinary  yeast.     The 
ferment  consists  of  small,  round  cells  arranged  in  chains.     The 
products  of  its  action  are  alcohol  and  carbon  dioxide. 

2.  Lactic   acid  fermentation.      This  is  due  to  a  vegetable 
ferment  which  is  contained  in  sour  milk.     It  has  the  power  of 
transforming  sugar  into  lactic  acid. 

3.  Acetic  acid  fermentation.     This  is  due  to  a  peculiar  vege- 
table ferment  which  acts  upon  alcohol,   transforming  it  into 
acetic  acid. 

The  germs  of  the  various  ferments  are  in  the  air ;  and,  when- 
ever they  find  favorable  conditions,  they  develop  and  produce 
their  characteristic  effects.  They  will  not  develop  in  a  solution 
of  pure  sugar.  The  variety  of  sugar  which  is  fermentable,  and 
which  is  the  one  from  which  alcohol  is  obtained,  is  not  our 
ordina^  cane  sugar,  but  one  known  as  grape  sugar ;  or,  more 
commonly,  glucose.  In  order  that  the  ferments  may  grow,  there 


FERMENTATION.  39 

must  be  present  in  the  solution,  besides  the  sugar,  substances 
which  contain  nitrogen.  These,  as  well  as  the  sugar,  are  con- 
tained in  the  juices  pressed  out  from  fruits,  and  hence  these 
juices  readily  undergo  fermentation. 

In  the  manufacture  of  alcohol  a  solution  containing  either 
starch  or  sugar  is  first  prepared  from  the  residue  of  wine  presses, 
or  from  some  kind  of  grain  or  potatoes.  In  case  the  solution 
contains  grape  sugar,  this  undergoes  fermentation  directly 
when  the  ferment  is  added.  If  the  substance  in  solution 
is  cane  sugar,  this  is  first  changed  by  the  ferment  into  grape 
sugar,  and  the  fermentation  then  takes  place  as  in  the  first 
case. 

Experiment  7.  Dissolve  40  to  50&  commercial  grape  sugar  in  2  to 
3  litres  of  water  in  a  good-sized  flask.  Connect  the  flask  by  means  of 
a  bent  tube  with  a  cylinder  containing  clear  lime  water.  Protect  the 
latter  from  the  air  by  means  of  a  tube  containing  caustic  potash.  Now 
add  to  the  solution  of  grape  sugar  a  little  brewer's  yeast;  close  the 
connections,  and  allow  to  stand.  Soon  an  evolution  of  gas  will  begin, 
and,  as  this  passes  through  the  lime  water,  a  precipitate  of  calcium 
carbonate  will  be  formed.  After  the  action  is  over,  place  the  flask  in 
a  water-bath ;  connect  with  a  condenser,  and  distil  over  100CC  of  the 
liquid.  Examine  this  for  alcohol. 

A.  good  way  to  detect  alcohol  is  this:  Warm  the  solution  to  be 
tested;  add  a  small  piece  of  iodine  and  then  caustic  potash  until  the 
color  is  destroyed.  On  cooling,  a  yellow  crystalline  powder  of  iodo- 
form  is  deposited. 

To  obtain  alcohol  from  fermented  liquids,  they  must  be  dis- 
tilled. The  ordinary  alcohol  contains  water,  and  a  mixture  of 
other  alcohols  called  fusel  oil.  The  latter  can  be  removed 
partly  by  distillation,  and  the  last  portions  can  be  gotten  rid  of 
by  filtering  through  charcoal.  The  water  cannot  be  removed 
completely  by  distillation,  though  a  product  containing  about 
93  per- cent  of  alcohol  can  be  obtained. 

Absolute  alcohol  is  ordinary  alcohol  from  which  the  water  has 
been  removed  to  a  considerable  extent  by  means  of  quicklime. 
As  a  rule  absolute  alcohol  contains  about  5  per  cent  of  water. 


40  DERIVATIVES   OF   METHANE   AND   ETHANE. 

By  continued  treatment  with  lime  the  quantity  of  water  may  be 
reduced  to  one-half  a  per  cent,  and  this  small  quantity  may  be 
removed  by  treatment  with  metallic  sodium. 

Experiment  8.  Prepare  absolute  alcohol  from  ordinary  strong 
alcohol.  For  this  purpose  a  good-sized  flask  is  one-half  to  two-thirds 
filled  with  quicklime  broken  into  small  lumps.  The  alcohol  is  poured 
upon  the  lime,  and  allowed  to  stand  at  least  twenty-four  hours,  when 
it  is  distilled  oft*  on  a  water-bath.  If  the  alcohol  used  contains  con- 
siderable water,  it  is  necessary  to  repeat  the  treatment  with  lime. 

Pure  ethyl  alcohol  has  a  peculiar,  pleasant  odor.  It  is 
claimed,  however,  that  perfectly  anhydrous  alcohol  has  no 
odor.  It  remains  liquid  at  very  low  temperatures,  but  has 
recently  been  converted  into  a  solid  at  a  temperature  of  —130.5°. 
It  boils  at  78.3°.  It  burns  with  a  non-luminous  flame,  which 
does  not  leave  a  deposit  of  soot  on  substances  placed  in  it.  It 
may  hence  be  used  for  heating  purposes  in  chemical  labora- 
tories. When  mixed  with  air  its  vapor  explodes  when  a  flame  is 
applied.  Its  effects  upon  the  human  system  are  well  known. 
It  intoxicates  when  taken  in  dilute  form,  while  in  large  doses  it 
is  poisonous.  It  lowers  the  temperature  of  the  body  from  0.5° 
to  2°  when  taken  internally,  although  the  sensation  of  warmth 
is  experienced. 

Alcohol  is  the  principal  solvent  for  substances  of  organic 
origin.  It  is  hence  extensively  used  in  the  arts,  as  in  the  manu- 
facture of  varnishes,  perfumes,  and  tinctures  of  drugs. 

The  many  beverages  which  are  in  use  depend  for  their  effi- 
ciency upon  the  presence  of  alcohol  in  greater  or  smaller  quantity. 
The  milder  forms  of  beer  contain  from  2  to  3  per  cent ;  light 
wines,  such  as  claret,  about  8  per  cent ;  while  whiskey,  brandy, 
rum,  and  other  distilled  liquors  sometimes  contain  as  much  as  CO 
to  75  per  cent.  These  distilled  liquors  are  nothing  but  ordinary 
alcohol  with  water  and  small  quantities  of  substances  obtained 
from  the  fruit  or  grain  used  in  their  preparation,  or  obtained  by 
standing  in  barrels  made  of  oak  wood.  The  different  flavors 
are  due  to  the  small  quantities  of  these  substances. 


FERMENTATIOK.  41 

Chemical  conduct  of  ethyl  alcohol.  All  that  was  said  in  regard 
to  the  chemical  conduct  of  methyl  alcohol  applies  to  ethyl 
alcohol.  The  action  of  acids,  of  phosphorus  trichloride,  of 
the  alkali  metals,  and  of  oxidizing  agents  is  the  same  as  in  the 
case  of  methyl  alcohol,  only  the  products  formed  contain  the 
radical,  ethyl,  C2H5,  instead  of  methyl. 

NOTE  FOR  STUDENT.  —  The  student  is  advised  to  write  the  equa- 
tions representing  the  action  of  hydrochloric,  hydrobromic,  and  nitric 
acids ;  of  phosphorus  trichloride ;  and  of  potassium,  upon  ethyl  alcohol. 
What  is  the  composition  of  the  acid  formed  by  oxidation  of  ordinary 
alcohol? 

2.  ETHERS. 

As  has  been  shown,  when  an  alcohol  is  treated  with  potas- 
sium or  sodium,  compounds  are  formed  having  the  for- 
mulas 

CH3ONa,  CH3OK,  C2H5OK,  C2H5ONa. 

If  one  of  these  be  treated  with  a  mono-halogen  derivative  of 
a  hydrocarbon,  as,  for  example,  iodo-methane,  CH3I,  reaction 
takes  place  thus  :  — 

CH3ONa  +  CH3I  =  C2H6O  +  Nal. 

The  reaction  leaves  very  little  room  for  doubt  in  regard  to 
the  structure  of  the  compound  CL,H6O.  It  must  be  represented 

PIT 

by  the  formula   CH3  -  O  -  CH3,   or  ^    3>O,    or   (CH3)2O. 

CH3 

Comparing  it  with  methyl  alcohol,  we  see  that  it  is  obtained 
from  the  alcohol  by  replacing  the  hydrogen  of  the  hydroxyl  by 
methyl,  CH3.  Just  as  the  alcohol  is  analogous  to  the  hydroxide 
KOH,  so  the  new  compound  is  analogous  to  the  oxide  K2O. 
It  is  the  representative  of  a  class  of  bodies  known  as  ethers, 
which  are  analogous  to  the  oxides  of  the  metals.  Our  ordinary 
ether  is  the  chief  representative  of  the  class. 

While  the  reaction  above  mentioned  serves  admirably  to  show 
the  relations  between  the  alcohols  and  ethers,  it  is  not  the  one 


42  DERIVATIVES   OF   METHANE  AND  ETHANE. 

that  is  made  use  of  in  their  preparation.    This  consists  in  treat- 
ing the  alcohols  with  sulphuric  acid,  and  distilling. 

Ethyl  ether,  C4H10O  =  (C2H5)2O.  —  This  is  the  substance 
commonly  known  simply  as  ether,  or  sulphuric  ether.  The  latter 
name  was  originally  given  to  it  because  sulphuric  acid  is  used 
in  its  manufacture,  and  plainly  not  because  any  sulphur  is  con- 
tained in  it. 

Theoretically,  the  simplest  way  to  make  ether  from  alcohol 
is  to  make  the  sodium  compound  of  alcohol,  C2H5ONa,  and  to 
heat  this  with  brom-  or  iodo-ethane  thus  :  — 

C2H5ONa  -f  C2H5I  =  (C2H5)2O  +  Nal.   ' 

Practically,  however,  ether  may  be  made  much  more  readily, 
and  it  is  made  on  the  large  scale  by  mixing  sulphuric  acid  and 
alcohol  in  certain  proportions,  and  then  distilling  the  mixture 
as  described  below.  Two  distinct  reactions  are  involved  in  this 
process.  First,  when  alcohol  and  sulphuric  acid  are  brought 
together,  half  the  hydrogen  of  the  acid  is  replaced  by  ethyl 
thus  :  — 

C2H5OH  +  ^  >  S04  =  °2^5  >  S04  +  H20. 
xl  H 

The  product  thus  formed  is  called  ethyl-sulphuric  acid. 

Experiment  9.  Slowly  pour  20  to  30CC  conceDtrated  sulphuric  acid 
into  about  the  same  volume  of  alcohol  of  80  to  90  per  cent.  Stir 
thoroughly,  and  dilute  with  a  litre  of  water.  In  an  evaporating  dish 
add  powdered  barium  carbonate  until  the  liquid  is  neutral.  Filter, 
and  examine  the  clear  filtrate  for  barium.  Its  presence  shows  that  a 
soluble  barium  salt  has  been  formed.  This  is  barium  ethyl-sulphate, 
Ba(C2H6S04)a. 

"When  ethyl-sulphuric  acid  is  heated  with  alcohol,  ether  is 
formed,  and  sulphuric  acid  is  regenerated  thus  :  — 

C2H5OH  +  °2?T5  >  S04  =  ^2H5  >Q  +  H  sc>4 

H  ^2^5 


ETHYL   ETHER. 


43 


The  ether  thus  formed  distils  over ;  and,  if  alcohol  be  admitted 
to  the  sulphuric  acid,  ethyl-sulphuric  acid  will  again  be  formed, 
and  with  excess  of  alcohol  it  will  yield  ether.  The  actual 
method  of  procedure  is  described  in 

Experiment  1O.  Arrange  an  apparatus  as  shown  in  Fig.  6.  In 
the  flask  put  a  mixture  of  200&  alcohol,  and  360^  ordinary  concen- 
trated sulphuric  acid.  It  is  better  to  mix  them  in  another  vessel, 
and  allow  the  mixture  to  stand  for  some  time  until  it  is  thoroughly 


i'll'li;  I'iiiliillllililiilillilliiliOT 

Fig.  6. 

cooled  down ;  and  then  to  pour  off  from  the  precipitated  lead  sulphate  as 
completely  as  possible.  Now  heat  until  the  thermometer  indicates  the 
temperature  140°.  At  this  point  the  mixture  boils,  and  ether  begins  to 
pass  over.  As  soon  as  this  is  noticed,  open  the  stop-cock  of  the  vessel 
A,  and  let  a  slow  stream  of  alcohol  pass  into  the  distilling  flask  through 
the  tube  J5,  which  must  reach  beneath  the  surface  of  the  mixture. 
Regulate  this  stream  so  that  the  temperature  remains  as  near  140°  as 
possible.  In  this  way  the  operation  can  be  kept  up  for  a  considerable 
time,  the  alcohol  admitted  to  the  flask  passing  out  as  ether,  and  being 
collected  together  with  some  alcohol  in  the  receiver.  After  about  a 
half  litre  to  a  litre  of  distillate  has  been  collected,  stop  the  operation. 
The  mixture  in  the  distilling  flask  may  be  kept  in  a  stoppered  bottle 
and  used  again  when  needed.  Pour  the  distillate  into  a  glass-stoppered 


44  DEBIVATIVES   OF   METHANE   AND   ETHANE. 

cylinder,  and  add  water.  The  ether  will  rise  to  the  top,  forming  a 
distinct  layer,  and  may  be  removed  by  means  of  a  pipette  or  separating 
funnel.  It  should  be  shaken  in  this  way  a  few  times  with  water;  then 
treated  with  a  little  calcium  chloride ;  and,  after  standing,  poured  off 
into  a  dry  flask,  and  distilled  on  a  water-bath. 

N.B.  Never  boil  ether  over  a  free  flame ;  and,  in  working  with  it, 
always  carefully  avoid  the  neighborhood  of  flames.  In  boiling  it  on  a 
water-bath,  do  not  heat  the  water  to  boiling. 

Ether  is  a  colorless,  mobile  liquid  of  a  peculiar  odor  and 
taste.  It  boils  at  34.9°.  (Hence  the  necessity  for  the  pre- 
cautions mentioned  above.)  Its  specific  gravity  is  0.736  at  0°. 
(What  evidence  have  you  had  that  it  is  lighter  than  water?) 
It  is  very  inflammable. 

Experiment  11.  Put  a  few  cubic  centimetres  of  ether  in  a  small 
evaporating  dish,  and  apply  a  flame. 

When  its  vapor  is  mixed  with  air,  the  mixture  is  extremely 
explosive.  Ether  is  somewhat  soluble  in  water,  and  water  is 
also  somewhat,  though  less,  soluble  in  ether ;  so  that  when  the 
two  are  shaken  together  the  volume  of  the  ether  becomes 
smaller,  even  though  every  precaution  is  taken  to  avoid  evapor- 
ation. Ether  mixes  with  alcohol  in  all  proportions.  It  is  a 
good  solvent  for  resins,  fats,  alkaloids,  and  many  other  classes 
of  carbon  compounds. 

It  is  an  excellent  anaesthetic,  and  is  used  extensively  in  this 
capacity.  In  consequence  of  its  rapid  evaporation,  it  is  used 
to  produce  cold,  as  in  the  manufacture  of  ice.  So,  also,  when 
brought  against  the  skin  in  the  form  of  spray,  the  cold  produced 
is  so  great  as  to  cause  insensibility. 

Experiment  12.  In  a  thin  glass  test-tube  put  5CC  water.  Introduce 
the  tube  into  a  small  beaker  containing  some  ether.  Force  air  through 
the  ether  by  means  of  a  bellows.  The  water  will  be  frozen. 

Chemical  conduct  of  ether.  If  we  were  dependent  upon  the 
decompositions  and  general  reactions  of  ether  for  our  knowledge 
of  its  structure,  we  would  be  left  in  grave  doubt  as  to  the  rela- 


MIXED   ETHERS.  45 

tions  existing  between  it  and  alcohol.  Its  decompositions  are 
mostly  deep-seated,  and  not  easily  explained.  Fortunately,  as 
we  have  seen,  its  synthesis  from  sodium  ethylate,  C2H5ONa,  and 
iodo-ethane,  C2II5I,  leaves  us  in  no  doubt  regarding  its  structure. 
The  simplest  decompositions  are  these  :  — 

Heated  with  water  and  a  small  quantity  of  sulphuric  acid  to 
150°,  it  is  converted  into  alcohol  :  — 

^5>0  +  ^>0  =  2C2H5OH. 

^2*15 

Treated  with  hydriodic  acid  at  a  low  temperature,  alcohol 
and  iodo-ethane  are  formed  :  — 

**  =  C2H5OH  +  C2H5I. 

25 

Mixed  ethers.  —  Just  as  ordinary  or  ethyl  alcohol  yields 
ethyl  ether,  so  methyl  alcohol  yields  methyl  ether,  (CH3)2O. 
By  modifying  the  method,  a  mixed  ether,  methyl-ethyl  ether, 

r1  TT 

2    5  >  O,  may  be  obtained.    This  is  formed  by  treating  sodium 
CH3 

methylate  with  iodo-ethane,  or  by  treating  sodium  ethylate  with 
iodo-methane  :  — 

CH3ONa  +  C2H5I  =  ^2H5  >  O  +  Nal  ; 
L/H3 

P  TT 

C2H5ONa  +   CH3I  =  *£*?  >  O  -f  Nal. 

di3 

It  is  formed  also  by  distilling  methyl  alcohol  with  ethyl-sul- 
phuric acid,  or  ethyl  alcohol  with  methyl-sulphuric  acid  :  — 


3  >  O  +     25  >  S04  =     *«  >  o  +  H2S04  ; 
CH3 

C2H5  >  Q  +   CH3  >  s()4  =  C2H5  >  Q  +  H2SQ4 

UJ:13 

Methyl  ether  and  methyl-ethyl  ether  are  very  similar  to  ordinary 
ether. 


46  DERIVATIVES   OF   METHANE  AND   ETHANE. 

3.    ALDEHYDES. 

It  has  been  stated  above  that  wjien  methyl  and  ethyl  alcohols 
are  oxidized,  they  are  converted  into  acids  having  the  formulas 
CH2O2  and  C2H4O2,  respectively.  By  proper  precautions,  prod- 
ucts can  be  obtained  intermediate  between  the  alcohols  and 
acids,  and  differing  from  them  in  composition  in  that  they 
contain  two  atoms  of  hydrogen  less  than  the  corresponding 
alcohols.  These  products  are  called  aldehydes,  from  alcohol 
dehydrogenatum,  from  the  fact  that  they  must  be  regarded  as 
alcohols  from  which  hydrogen  has  been  abstracted.  The  rela- 
tions in  composition  between  the  hydrocarbons,  alcohols,  and 
aldehydes  are  shown  by  these  formulas  :  — 

Hydrocarbons  Alcohols.  Aldehydes. 

CH4  CH,0  CH20 

C2H6  C2H60  C2H40 

etc.  etc.  etc. 

Methyl  aldehyde,  formic  aldehyde,  CH2O.  —  This  is 
made  by  gentle  oxidation  of  methyl  alcohol,  as  by  passing  the 
vapor  of  the  alcohol  with  air  over  a  heated  platinum  spiral.  It 
is  a  very  volatile  liquid,  which,  up  to  the  present,  has  not  been 
prepared  in  pure  condition. 

In  order  to  gain  a  clear  insight  into  the  nature  of  the  alde- 
hydes, it  will  be  best  to  study  the  best-known  representative  of 
the  class,  which  is  ethyl  aldehyde. 

Ethyl  aldehyde,  acetic  aldehyde,  C2H4O.  —  The  name 
ethyl  aldehyde  is  intended  to  recall  the  connection  between  the 
substance  and  ethyl  alcohol ;  while  the  name  acetic  aldehyde  is 
given  to  it  because,  by  further  oxidation,  it  is  converted  into 
acetic  acid.  The  latter  is  perhaps  the  better  name,  as  the  alde- 
hyde really  does  not  contain  ethyl,  C2H5,  as  is  evident  from  its 
molecular  formula. 

Acetic  aldehyde  is  formed  whenever  alcohol  is  brought  in 


LIBRARY 
COLLEGE  OF 

*£251e3?y         ACETIC   ALDEHYDE.  47 

contact  with  an 'oxidizing  mixture;  as,  for  example,  potassium 
bichromate  and  dilute  sulphuric  acid. 

Experiment  13.  Dissolve  a  little  potassium  bichromate  in  water, 
and  add  sulphuric  acid.  Now  add  a  few  cubic  centimetres  of  alco- 
hol, and  notice  the  odor  which  is  that  of  aldehyde.  Notice,  also, 
the  change  of  color  of  the  solution,  showing  the  reduction  of  the 
chromate. 

As  aldehyde  is  a  very  volatile  liquid,  it  is  difficult  to  collect  it. 
In  preparing  it,  it  is  therefore  better  to  pass  it  into  some  liquid 
which  will  absorb  it,  and  then  afterwards  separate  it  by  some 
appropriate  method.  A  good  method  is  that  described  below. 

Experiment  14.  Arrange  an  apparatus  as  shown  in  Fig.  7.  Put 
120s  granulated  potassium  bichromate  in  the  flask  A,  which  must  have 
a  capacity  of  1£  to  2  litres.  Make  a  mixture  of  IQQs  concentrated  sul- 


~r 


Fig.  7. 

phuric  acid,  480s  water,  and  120s  alcohol.  Cool  the  mixture  down  to 
the  ordinary  temperature,  and  then  pour  it  slowly  through  the  funnel- 
tube  B  into  the  flask  containing  the  potassium  bichromate.  The 


48  DERIVATIVES   OF   METHANE   AND   ETHANE. 

flask  should  stand  on  a  water-bath  containing  cold  water.  The  cylin- 
ders C  and  D  are  about  half  filled  with  ordinary  ether,  each  one  con- 
taining about  200CC  ether,  and  placed  in  the  large  vessel  F,  which 
contains  ice  water. 

Usually,  when  the  alcohol,  water,  and  sulphuric  acid  are  poured  upon 
the  bichromate,  the  action  begins  without  application  of  heat.  At  times 
it  takes  place  rapidly,  so  that  the  liquid  should  always  be  added  slowly. 
The  aldehyde  which  is  thus  formed,  together  with  some  alcohol  and 
water  vapor,  passes  into  the  condenser-tube,  where  the  greater  part  of 
the  alcohol  and  water  is  condensed  and  returned  to  the  flask,  while 
the  aldehyde,  being  much  more  volatile,  passes  into  the  ether  and  is 
there  absorbed.  After  the  action  is  over,  the  distilling  vessel  and  con- 
denser are  removed,  and,  at  E,  connection  is  made  with  an  apparatus 
furnishing  dry  ammonia  gas.  The  gas  is  passed  into  the  cold  ethereal 
solution  of  aldehyde  to  the  point  of  saturation.  A  beautifully  crystal- 
lized compound  of  aldehyde  and  ammonia,  known  as  aldehyde-ammonia, 
is  deposited.  The  ether  is  poured  off,  and  the  crystals  placed  on  filter- 
paper.  They  gradually  undergo  change  in  the  air,  becoming  yellow, 
and  acquiring  a  peculiar  odor.  If  the  crystals  are  placed  in  a  flask  and 
treated  with  dilute  sulphuric  acid,  pure  aldehyde  passes  over,  and  may 
be  condensed  by  ice-cold  water. 

In  the  process  of  purification  of  ordinary  alcohol  it  is  filtered 
through  charcoal.  It  is  thus  partly  oxidized  to  aldehyde  ;  and, 
when  it  is  afterwards  distilled,  the  first  portions  which  pass 
over  contain  aldehyde,  which  is  obtained  on  the  large  scale  by 
repeated  distillation  of  these  "  first  runnings." 

Aldehyde  is  a  colorless  liquid,  boiling  at  21°.  It  mixes  with 
water  and  alcohol  in  all  proportions.  Its  odor  is  marked  ana 
characteristic. 

From  the  chemical  stand-point,  the  most  characteristic  prop- 
erty of  aldehyde  is  its  power  to  unite  directly  with  other  sub- 
stances. It  unites  with  ox3Tgen  to  form  acetic  acid ;  with 
hydrogen  to  form  alcohol ;  with  ammonia  to  form  aldehyde- 
ammonia,  C2H4O.]S[H3 ;  with  hydrocyanic  acid  to  form  alde- 
hyde hydrocyanide,  C2H4O.HCN ;  with  the  acid  sulphites  of 
the  alkalies  forming  compounds  represented  by  the  formulas 
C2H4O.HKSO3  and  C,H4O.HNaS03 ;  and  with  other  substances. 
Indeed,  if  left  to  itself,  it  readily  changes  into  polymeric  modi- 


METALDEHYDE.  49 

fications,   uniting   with   itself    to   form  more    complex  bodies, 
paraldehyde  and  metaldehyde. 

Paraldehyde,  C6Hr2O;!.  —  This  is  formed  by  adding  a  few 
drops  of  concentrated  sulphuric  acid  to  aldehyde,  which  causes 
the  liquid  to  become  hot.  On  cooling  to  0°,  the  paraldehyde 
solidifies  in  crystalline  form.  It  melts  at  10.5°.  It  dissolves 
in  eight  times  its  own  volume  of  water.  Boils  at  124°.  When 
distilled  with  dilute  sulphuric  acid,  hydrochloric  acid,  etc.,  it  is 
converted  into  aldehyde.  The  specific  gravity  of  its  vapor  has 
been  found  to  be  4.583.  This  leads  to  the  molecular  weight 
132.4,  and  consequently  to  the  formula  C6H12O3.  It  is  called  a 
polymeric  modification  of  aldehyde.  The  cause  of  the  peculiar 
action,  and  the  structure  of  the  product  are  not  known. 

Metaldehyde,  (C2H4O)X. — Metaldehyde  is  formed  in  much 
the  same  way  as  paraldehyde,  only  a  low  temperature  (below 
0°)  is  most  favorable  for  its  formation.  It  cr\'stallizes  in  needles, 
which  are  insoluble  in  water,  and  but  slightly  soluble  in  alcohol, 
chloroform,  and  ether  in  the  cold,  though  more  readily  at  a 
slightly  elevated  temperature.  When  heated  to  120°  in  a  sealed 
tube,  it  is  converted  into  aldehyde.  Hence  its  vapor  density 
cannot  be  determined,  and  its  molecular  weight  is  unknown. 
It  has  the  same  composition  as  aldehyde  and  paraldehyde, 
but  it  is  probably  more  complex  than  the  latter ;  that  is,  its 
molecule  is  probably  made  up  of  a  larger  number  than  three 
molecules  of  aldehyde.  Distilled  with  dilute  sulphuric  acid, 
etc.,  it  is  easily  converted  into  aldehyde. 

In  consequence  of  the  tendency  of  aldehyde  to  unite  with 
oxygen,  it  is  a  strong  reducing  agent.  When  added  to  an 
ammoniacal  solution  of  silver  nitrate,  metallic  silver  is  deposited 
on  the  walls  of  the  vessel  in  the  form  of  a  brilliant  mirror. 

Experiment  lo.  To  a  weak  aqueous  solution  of  aldehyde,  or  of 
aldehyde-ammonia,  in  a  test-tube,  add  a  few  drops  of  ammonia  and  of 
a  solution  of  silver  nitrate.  Warm  gently ;  and,  when  the  deposit  on 


50  DERIVATIVES   OF   METHANE   AND   ETHANE. 

the  walls  of  the  tube  begins  to  appear,  stop  heating.  A  brilliant  mirror 
of  metallic  silver  will  appear.  This  method  is  used  in  the  manufac- 
ture of  mirrors.  What  becomes  of  the  aldehyde? 

Chemical  transformations  of  aldehyde.  As  aldehyde  is  pro- 
duced from  alcohol  by  oxidation,  so  alcohol  can  be  formed 
from  aldehyde  by  reduction  :  — 

C2H6O  +  O    =  C2H4O  +  H2O  ; 

C2H4O  +  H2  =  C2H6O. 

By  oxidation  aldehyde  is  converted  into  an  acid  of  the  formula 
C2H4O2,  which  is  acetic  acid ;  and,  by  reduction,  acetic  acid  is 
converted  into  aldehyde  :  — 

C2H40   +  O    =  C2H402 ; 

C2H4O2  +  H2  =  C,H4O  +  H2O. 

Treated  with  phosphorus  pentachloride,  aldehyde  yields  ethyl- 
idene  chloride,  C2H4C12  (which  see).  This  reaction  is  of  special 
interest  and  importance,  as  it  helps  us  to  understand  the  relation 
between  aldehyde  and  alcohol.  Alcohol,  as  has  been  shown, 
is  the  hydroxide  of  ethyl,  C2H5.OH.  When  oxidized  it  loses 
two  atoms  of  hydrogen.  Is  the  hydrogen  of  the  hydroxyl 
one  of  the  two  which  are  given  off?  If  so,  what  readjustment 
of  the  ox}'gen  takes  place?  Such  are  the  questions  which  we 
have  a  right  to  ask. 

To  understand  the  action  of  phosphorus  pentachloride  on 
aldehyde,  it  will  be  necessary  to  consider  briefly  the  action  of 
this  reagent  in  general  upon  compounds  containing  oxygen. 
When  it  is  brought  in  contact  with  water,  the  first  change  is 
represented  by  the  equation 

H20  +  PC15     =  POCL  +  2  HC1. 
Next,  the  oxichloride,  POC13,  is  acted  upon  thus  :  — 

3  H2O  -f  POC13  =  PO(OH)3  +  3  HC1. 

Or,  expressing  both  changes  in  one  equation,  we  have :  — 

4  H2O  +    PC15    =  PO(OH)3  +  5  HC1. 


ALDEHYDE.  51 

The  phosphorus  pentachloride  gives  up  its  chlorine  and  takes 
up  oxygen,  or  oxygen  and  hydrogen,  in  its  place.  This  is  the 
general  tendency  of  the  chlorides  of  phosphorus. 

Now,  when  a  chloride  of  phosphorus  is  brought  together  with 
an  alcohol,  the  oxygen  is  replaced  by  chlorine,  two  atoms  of 
the  latter  for  one  of  the  former,  thus  :  — 

C2H5.OH  +  PC15  -  C2H5C1.C1H  +  POC13. 

But  as  hydrox}'!,  —  O  —  H,  is  univalent,  its  place  cannot  be 
taken  by  two  atoms  of  chlorine  and  one  of  hydrogen,  and  the 
two  chlorine  atoms  have  not  the  power  of  linking  the  hydrogen 
to  the  ethyl.  Hydrochloric  acid  is  given  off,  and  a  compound  is 
formed,  which  may  be  regarded  as  alcohol  in  which  one  chlorine 
atom  takes  the  place  of  the  hydroxyl.  This  is  the  kind  of 
action  which  takes  place  whenever  a  chloride  of  phosphorus  acts 
upon  a  compound  containing  hydroxyl ;  and  we  hence  make  use 
of  the  reaction  for  determining  whether  hydroxyl  is  or  is  not 
present  in  a  compound. 

When  aldehyde  is  treated  with  phosphorus  pentachloride,  the 
action  is  entirely  different  from  that  just  described.  Instead  of 
a  hydrogen  and  an  oxygen  atom  being  replaced  by  one  chlo- 
rine, the  oxygen  atom  alone  is  replaced  by  two  chlorine  atoms :  — 

C2H40  +  PC15  =  C2H4C12  +  POC13. 

If  the  explanation  above  offered  of  the  action  of  phosphorus 
pentachloride  on  alcohol  is  correct,  it  follows  that  aldehyde  is 
not  a  hydroxyl  compound.  We  can  readily  understand  why  the 
oxygen  atom  should  be  replaced  by  two  chlorine  atoms,  if  it 
is  in  combination  only  with  carbon  as  in  carbon  monoxide,  CO. 
There  is  an  essential  difference  between  this  kind  of  combina- 
tion and  that  which  we  have  in  hydroxyl  as  C  —  O  —  H.  In 
the  latter  condition  the  oxygen  serves  to  connect  carbon  with 
hydrogen ;  in  the  former  it  is  in  combination  only  with  the 
carbon,  and,  presumably,  the  force  which  holds  it  can  also  hold 
two  atoms  of  chlorine  or  of  any  other  univalent  element  with 


52  DERIVATIVES   OF   METHANE   AND   ETHANE. 

which  it  can  unite.  So  that,  if  oxygen  be  in  a  compound  in 
the  carbon  monoxide  condition,  we  would  expect  it  to  be  re- 
placed by  two  atoms  of  chlorine  when  the  compound  is  treated 
with  phosphorus  pentachloride.  Let  R.CO  represent  any  such 
compound  ;  then  we  would  have  :  — 

RCO  +  PC15  =  R.CC12  +  POC13 ; 

while,  when  oxygen  is  present  in  the  hydroxyl  condition,  we 
have : — 

R.C-O-H  +  PC15  =  R.CC1  +  POC13  -f  HC1. 

Just  as  the  latter  reaction  is  used  to  detect  the  presence  of 
hydroxyl  oxygen,  so  the  former  is  used  to  detect  oxygen  in  the 
other  condition,  which  is  commonly  known  as  the  carbonyl  con- 
dition. 

In  terms  of  the  valence  hypothesis,  it  is  said  that  in  the 
hydroxyl  compounds  oxygen  is  in  combination  with  carbon  with 
one  of  its  affinities,  and  with  hydrogen  with  the  other,  while  in 
the  carbonyl  compounds  it  is  in  combination  with  carbon  with 
both  its  affinities  as  represented  thus,  C=  O. 

According  to  the  above  reasoning  aldehyde  is  a  carbonyl 
compound,  or  it  contains  the  group  CO.  The  simplest  alde- 
hyde must  therefore  be  represented  by  the  formula  H9C  =  O. 

O 
II 

Its  homologue,  acetic  aldehyde,  is  CH3.C  — H.    The  peculiar  prop- 
erties of  aldehyde  are  believed  to  be  due  to  the  presence  of  this 
O 
li 
group,  C  — H,  which  is  called  the  aldehyde  group.     We  do  not 

know  that  the  double  line  in  the  formula  conveys  any  correct 
idea  in  regard  to  the  relation  between  the  carbon  and  oxygen. 
All  that  we  know  is  that  these  two  elements  do  occur  in  two 
different  relations  to  each  other,  and  the  formulas  C  —  O  —  H 
and  C  =  O  recall  these  relations.  They  are  expressions  of  facts 
established  by  experiment.  Our  notions  in  regard  to  these 
relations  are  largely  dependent  upon  the  reactions  with  the 
chlorides  of  phosphorus  referred  to  above. 


CHLORAL.  53 

Chloral,  trichloraldehyde,  CC13  .CHO.  — -  When  chlorine 
acts  directly  upon  aldehyde,  complicated  reactions  take  place 
which  need  not  be  considered  here.  If,  however,  water  and 
calcium  carbonate  are  present,  substitution  takes  place,  and 
trichloraldehyde  is  formed.  When  alcohol  is  treated  with 
chlorine,  a  double  action  takes  place :  1st.  The  alcohol  is 
changed  to  aldehyde  thus : — 

CH3.CH2OH  +  C12  =  CH3.COH  +  2  HC1. 

Then  the  chlorine  acts  upon  the  aldehyde,  replacing  the  three 
hydrogens  of  the  methyl,  forming  trichloraldehyde  :  — 

CH3.COH  +  6  Cl  =  CC13.COH  +  3  HC1. 

In  reality  the  aldehyde  first  formed  acts  upon  the  alcohol, 
forming  an  intermediate  product  which  is  acted  upon  by  the 
chlorine.  The  chlorine  product  thus  formed  breaks  up,  forming 
chloral.  The  essential  features  of  the  reaction,  however,  are 
stated  in  the  above  equations.  Trichloraldehyde  is  the  sub- 
stance commonly  known  as  chloral.  It  is  simply  the  tri-chlo- 
rine  substitution  product  of  aldehyde.  It  has  all  the  general 
properties  of  aldehyde,  and  the  conclusion  is  therefore  justified 

O 

II 
that  it  contains  the  aldehyde  group  —  CH. 

Chloral  is  a  colorless  liquid,  which  boils  at  94°,  and  has  the 
specific  gravity  1.5. 

NOTE  FOR  STUDENT.  —  Give  the  formulas  of  compounds  formed 
when  chloral  is  brought  together  with  ammonia,  hydrocyanic  acid,  and 
the  acid  sulphites  of  the  alkalies.  What  is  the  formula  of  the  acid 
formed  by  its  oxidation?  The  answer  is  given  in  the  statement  that 
the  general  chemical  conduct  of  chloral  is  the  same  as  that  of  aldehyde. 

When  chloral  and  water  are  brought  together,  they  unite  to 
form  a  crystallized  compound,  chloral  hydrate,  C2HC13O  +  H2O, 
which  is  easily  soluble  in  water,  and  crystallizes  from  the  solu- 
tion in  beautiful,  colorless,  mouoclinic  prisms.  It  melts  at 46°, 


54  DERIVATIVES   OF  METHANE   AND   ETHANE. 

Taken  internally  in  doses  of  from  1.5  to  5g,  it  produces  sleep. 
In  larger  doses  it  acts  as  an  anaesthetic. 

When  treated  with  an  alkali,  chloral  and  chloral  hydrate 
break  up,  yielding  chloroform  and  formic  acid  :  — 

CClg.COH  +  KOH  =  CHC13  +  KCHO2. 

Chloral.  Chloroform.       Potassium 

formate. 

This  reaction,  taken  together  with  those  which  give  chloral 
from  alcohol,  enables  us  to  understand  the  reaction  which  is 
used  in  making  chloroform  and  iodoform. 

NOTE  FOR  STUDENT. — How  is  chloroform  made?  How  may  the 
method  be  explained?  Answer  the  same  questions  for  iodoform.  The 
bleaching  powder  used  in  preparing  chloroform  furnishes  chlorine.  Is 
an  alkali  present? 

4.  ACIDS. 

When  methyl  and  ethyl  alcohols  are  oxidized,  they  are  con- 
verted first  into  aldelrydes,  and  then  the  aldehydes  take  up 
oxygen  and  are  converted  into  acids.  The  relations  in  compo- 
sition between  the  hydrocarbons,  alcohols,  aldehydes,  and  acids 
are  shown  in  the  subjoined  table  :  — 

Acids. 

CH2O2 

C2H402 

etc. 

The  two  acids  whose  formulas  are  here  given  are  the  well- 
known  substances,  formic  and  acetic  acids. 


Formic  acid,  CH2O2.  —  This  acid  occurs  in  nature  in  red 
ants,  in  stinging  nettles,  in  the  shoots  of  some  of  the  varieties 
of  pine,  and  elsewhere. 

It  may  be  prepared  by  distilling  red  ants,  but  is  best  prepared 
by  heating  oxalic  acid  with  glycerin.  Oxalic  acid  has  the 


Hydrocarbons. 

Alcohols. 

Aldehydes. 

CH4 

CH40 

CH20 

C2H6 

C2H60 

C2H4O 

etc. 

etc. 

etc. 

FORMIC   ACID.  55 

composition  represented  by  the  formula  C2H2O4.  When  heated 
in  glycerin,  the  effect  is  to  break  it  up  into  carbon  dioxide  and 
formic  acid :  — 

C2H204  =  C02  +  CH202. 

The  formic  acid  distils  over,  and  may  be  condensed. 

Experiment  16.  Into  a  flask  of  500  to  600CC  capacity  put  200  to 
300CC  anhydrous  glycerin,  and  then  add  30  to  40s  crystallized  oxalic 
acid.  Connect  the  flask  with  a  condenser,  and  insert  a  thermometer 
through  the  cork  so  that  the  bulb  is  below  the  surface  of  the  glycerin. 
Heat  gently.  When  the  temperature  reaches  75°  to  90°,  carbon  dioxide 
will  be  given  off.  Dilute  formic  acid  then  distils  over.  When  the 
evolution  of  carbon  dioxide  stops,  add  another  portion  of  crystallized 
oxalic  acid,  and  heat  again.  This  operation  may  be  repeated  a  num- 
ber of  times  without  renewing  the  glycerin;  but,  when  about  100s  of 
oxalic  acid  have  been  decomposed,  enough  formic  acid  for  the  purpose 
will  have  been  formed.  Dilute  the  distillate  to  about  half  a  litre,  and, 
while  gently  warming  it  in  an  evaporating  dish,  add  freshly  precipi- 
tated and  washed  copper  oxide  in  small  quantities  until  no  more  is 
dissolved.  Then  filter,  and  evaporate  the  solution  to  crystallization. 
The  beautifully  crystallized  salt  thus  obtained  is  copper  formate. 

The  formation  of  formic  acid  by  oxidation  of  methyl  alcohol, 
and  by  treatment  of  chloral  with  an  alkali,  has  already  been 
mentioned.  The  following  methods  are  of  special  interest :  — 

(1)  By  the  action  of  carbon  monoxide  upon  potassium  hy- 
droxide :  — 

CO  +  KOH  =  H.CO2K. 

This  method  may  be  used  for  the  preparation  of  formic  acid  on 
the  large  scale.  Soda-lime  acts  as  well  as  potassium  hydroxide. 

(2)  By  the  action  of  metallic  potassium  upon  moist  carbon 
dioxide  (carbonic  acid)  :  — 

2  CO2  +  K2  +  H2O  =  HCO2K  -f  HCO3K, 
or  2  CO3H2  +  K2  ==  HCO2K  +  HCO3K  +  H2O. 


56  DERIVATIVES    OF   METHANE   AND   ETHANE. 

(3)  By  treatment  of  a  solution  of  ammonium  carbonate  with 
sodium  amalgam :  — 

C03(NH4)2  +  2  H  =  HC02(NH4)  +  H2O  +  NH3, 
and     HC02(NH4)  +  NaOH  =  HCO2Na  +  NH3  +  H2O. 

According  to  these  last  two  methods  formic  acid  appears  as  a 
reduction  product  of  carbonic  acid  formed  by  the  abstraction  of 
one  atom  of  oxygen  :  — 

H2CO3  =  H2CO2  +  O. 

It  is  extremely  important  to  bear  this  fact  in  mind,  as  it  is  of 
great  assistance  in  enabling  us  to  understand  the  relation  exist- 
ing between  the  two  acids,  and  between  them  and  all  other  acids 
of  carbon.  It  will  be  shown  that  all  the  acids  of  carbon  may 
be  regarded  as  derivatives  of  either  formic  acid  or  carbonic 
acid. 

(4)  When  hydrocyanic  acid  is  left  in  the  presence  of  an  acid 
or  an  alkali,  it  breaks  up,  forming  ammonia  and  formic  acid. 
The  reaction  may  be  represented  thus  :  — 

HCN  +  2  H2O  =  H2CO2  +  NH3. 

Of  course,  if  an  acid  is  present,  the  ammonium  salt  of  the  acid  is 
formed ;  and,  if  an  alkali  is  present,  the  formate  of  this  alkali  is 
formed.  A  reaction  similar  to  this  is  used  very  extensively  in  the 
preparation  of  the  acids  of  carbon,  as  will  be  shown. 

Anhydrous  formic  acid  may  be  made  by  dehydrating  either 
the  copper  or  lead  salt,  and  passing  dry  hydrogen  sulphide  over 
the  salt  placed  in  a  heated  tube.  The  acid  distils  over,  and 
may  be  obtained  perfectly  pure  by  placing  a  little  of  the  anhy- 
drous salt  in  it  and  redistilling. 

It  is  a  colorless  liquid  which  boils  at  99.9°.  It  has  a  pene- 
trating odor.  Dropped  on  the  skin,  it  causes  extreme  pain  and 
produces  blisters.  Its  specific  gravity  at  0°  is  1.22.  When 
cooled  down  it  solidifies  to  a  mass  of  crystals  which  melt  at  8.6°. 


ACETIC   ACID.  57 

Concentrated  sulphuric  acid  decomposes  it  into  carbon  mon- 
oxide and  water :  — 

H2CO2  =  CO  +  H2O. 

It  is  easily  oxidized  to  carbonic  acid.  Hence  it  acts  as  a 
reducing  agent.  Heated  with  the  oxides  of  mercury  or  silver, 
they  are  reduced  to  the  metallic  condition  :  — 

HgO  +  H2CO2  =  Hg  +  H2O  +  CO2. 

Like  other  acids,  formic  acid  yields  a  large  number  of  salts  with 
bases,  and  ethereal  salts  or  compound  ethers  with  the  alcohols. 
These  derivatives  need  not  be  considered  here.  The  salts  are 
all  soluble  in  water,  and  some  of  them,  as  the  lead,  copper,  and 
barium  salts,  crystallize  very  well.  Some  of  the  compound 
ethers  will  be  mentioned  when  these  substances  are  considered 
as  a  class. 

Acetic  acid,  C2H4O2.  —  The  two  methods  by  which  acetic 
acid  is  exclusively  made  are,  -»- 

(1)  By  the  oxidation  of  alcohol ;  and 

(2)  By  the  distillation  of  wood. 

"When  pure  alcohol  is  exposed  to  the  air  it  undergoes  no 
change.  If,  however,  some  platinum  black  be  placed  in  it, 
oxidation  takes  place  and  acetic  acid  is  formed.  So  also  if 
fermented  liquors  which  contain  nitrogenous  substances  be 
exposed  to  the  air,  oxidation  takes  place,  and  the  liquor  becomes 
sour  in  consequence  of  the  formation  of  acetic  acid.  A  great 
deal  of  acetic  acid  is  made  by  exposing  poor  wine  to  the  action 
of  the  air.  The  product  is  known  as  wine  vinegar.  The  for- 
mation of  vinegar  has  been  shown  to  be  due  to  the  presence  of 
a  microscopic  organism  (Mycoderma  aceti)  commonly  known  as 
"  mother-of -vinegar."  This  serves  in  some  way  to  convey  the 
oxygen  from  the  air  to  the  alcohol.  The  "  quick- vinegar 
process,"  much  used  \\\  the  manufacture  of  vinegar,  consists  in 
allowing  weak  spirits  of  wine  to  pass  slowly  through  barrels 


58  DERIVATIVES   OF  METHANE   AND   ETHANE. 

filled  with  beech  shavings  which  have  become  covered  with 
Mycoderma  aceti.  The  presence  of  the  organism  is  secured  by 
first  pouring  strong  vinegar  into  the  barrels,  and  allowing  it  to 
stand  for  one  or  two  days  in  contact  with  the  shavings. 

When  wood  is  distilled,  a  very  complex  mixture  passes  over, 
one  of  the  constituents  being  acetic  acid.  By  keeping  the  tem- 
perature down  comparatively  low,  the  amount  of  acetic  acid 
obtained  is  increased.  The  distillate  is  neutralized  with  soda 
ash,  and  the  solution  of  crude  sodium  acetate  thus  obtained 
evaporated  to  dryness.  It  is  then  treated  with  sulphuric  acid, 
and  distilled,  when  acetic  acid  passes  over. 

Besides  the  two  methods  mentioned,  there  are  two  others 
which  may  be  used  for  making  acetic  acid.  One  of  them  is  a 
modification  of  a  method  referred  to  under  formic  acid,  and, 
from  the  scientific  stand-point,  both  are  of  great  interest. 
They  are, — 

(1)  By   treating   carbon   dioxide  with   a  compound  known 
as  sodium-methyl,  which   may  be   regarded   as   marsh  gas,  in 
which  one  hydrogen  is  replaced  by  sodium  as  shown  in  the 
formula  CH3Na. 

CO2  +  CH3Na  =*  CH3.CO2Na. 

(2)  By  treating  methyl  cyanide,  CH3CN,  with  an  acid  or  an 
alkali :  — 

CH3CN  +  2H2O  =  CH3.CO2H  +  NH3. 

This  reaction  is  analogous  to  that  involved  in  the  formation 
of  formic  acid  from  hydrocyanic  acid  (see  p.  56) . 

Whether  the  acid  is  made  from  alcohol  or  from  wood,  it  must 
be  purified.  For  this  purpose  it  is  passed  through  charcoal  and 
distilled.  It  still  contains  water,  from  which  it  cannot  be 
completely  separated  by  distillation.  When  cooled  down  to  a 
sufficiently  low  temperature  it  solidifies,  and  the  water  may 
then  partly  be  poured  off.  By  repeating  the  freezing,  and 
distilling  a  few  times,  perfectly  pure,  anhydrous  acetic  acid 
may  be  obtained. 


ACETIC   ACID.  59 

Experiment  17.  Make  pure  acetic  acid  from  the  commercial  sub- 
stance. First  distil  in  fractions  until  a  portion  is  obtained  that  boils 
between  110°  and  119°.  Put  the  vessel  containing  this  in  ice.  The 
liquid  will  solidify  almost  completely.  Pour  off  the  little  liquid  which 
remains,  and  distil. 

Acetic  acid  is  a  clear,  colorless  liquid,  which  boils  at  119°. 
It  has  a  very  penetrating,  pleasant,  acid  odor,  and  a  sharp  acid 
taste.  The  pure  substance  acts  upon  the  skin  like  formic  acid, 
causing  pain  and  raising  blisters.  It  solidifies  when  cooled  down, 
and  the  crystals  melt  at  16.7°.  The  pure  acid  which  is  solid  at 
temperatures  below  16°  is  known  as  glacial  acetic  acid.  Its  speci- 
fic gravity  is  1.08  at  0°.  It  mixes  with  water  in  all  proportions. 

Acetic  acid  is  extensively  used,  chiefly  in  the  dilute,  impure 
form  known  as  vinegar.  Formic  acid  would  answer  perhaps  as 
well.  It  is  used  in  calico  printing  in  the  form  of  iron  and  alu- 
minium salts.  With  iron  it  gives  hydrogen,  which  is  needed  in 
the  manufacture  of  certain  compounds  used  in  making  dyes,  as, 
for  example,  aniline.  It  is  an  excellent  solvent  for  many 
organic  substances,  and  is  therefore  frequently  used  in  sci- 
entific researches. 

Derivatives  of  acetic  acid.  Acetic  acid  yields  a  very  large 
number  of  derivatives.  They  may  be  considered  briefly  under 
two  heads  :  ( 1 )  Those  which  are  formed  in  consequence  of  the 
acid  properties  and  which  necessitate  a  loss  of  the  acid  proper- 
ties, as  the  salts,  ethereal  salts,  etc.  ;  and  (2)  those  in  which 
the  acid  properties  remain  unchanged. 

Salts  of  acetic  acid.  The  acetates  of  the  alkalies  were  the 
first  compounds  of  carbon  ever  prepared.  The  potassium  and 
sodium  salts  are  used  in  the  chemical  laboratory.  Both  crystal- 
lize, the  sodium  salt  particularly  well  and  easily. 

Lead  acetate,  (C2H3O2)2Pb.  This  salt,  which  is  commonly 
known  as  sugar  of  lead,  is  made  on  the  large  scale  b}r  dissolv- 
ing lead  oxide  in  acetic  acid.  It  crystallizes  well,  and  is  solu- 
ble in  1.5  parts  of  water  at  ordinary  temperatures.  Commer- 
cial sugar  of  lead  frequently  contains  an  excess  of  lead  oxide  in 


60  DERIVATIVES    OF   METHANE   AND   ETHANE. 

the  form  of  basic  salts.  A  solution  of  such  a  mixture  becomes 
turbid  when  allowed  to  stand  in  the  air,  or  gives  a  precipitate 
when  dissolved  in  ordinary  spring  water,  in  consequence  of  the 
formation  of  lead  carbonate. 

Copper  acetate,  (C2H3O2)2Cu.  This  salt  may  be  made  by 
dissolving  copper  hydroxide  or  carbonate  in  acetic  acid.  It 
crystallizes  in  dark-blue,  transparent  prisms.  A  basic  acetate, 
formed  by  the  action  of  acetic  acid  on  copper  in  the  air,  is 
known  as  verdigris. 

Copper  aceto-arsenite,  3  CuAs2O4  +  (C2H302)2Cu.  This  double 
salt  is  formed  by  boiling  verdigris  and  arsenic  trioxide  together 
in  water.  It  has  a  fine  bright-green  color,  and  is  used  as  a 
coloring  matter.  It  is  the  chief  constituent  of  emerald  green, 
or  Schweinfurt's  green. 

Iron  forms  two  distinct  salts  with  acetic  acid,  the  ferrous 
salt,  (C2H3O2)2Fe  -f  4  H2O,  and  the  ferric  salt,  (C2H3O2)6Fe2. 
The  latter  is  formed  when  sodium  acetate  is  added  to  an  acidi- 
fied solution  of  a  ferric  salt.  At  first  the  solution  becomes 
deep-red  in  color ;  but,  on  boiling,  all  the  iron  is  precipitated 
as  a  basic  salt.  Hence  this  salt  is  used  for  the  purpose  of  sep- 
arating iron  from  manganese  in  analytical  operations. 

Experiment  18.  To  a  dilute  solution  of  ferric  chloride,  contained 
in  a  small  flask,  add  a  little  sulphuric  acid  and  a  solution  of  sodium 
acetate.  Boil  the  red  solution,  and  the  basic  iron  salt  is  precipitated, 
leaving  the  solution  colorless.  Filter,  and  examine  the  filtrate  for  iron. 

The  ethereal  salts  will  be  mentioned  briefly  when  this  class 
of  bodies  is  considered.  The  principal  one  is  ethyl  acetate  or 
acetic  ether,  which  is  formed  from  acetic  acid  and  ordinary  alco- 
hol. When  a  mixture  of  these  two  substances  is  treated  with 
sulphuric  acid,  the  ether  is  formed  and  may  be  recognized  by 
its  pleasant  odor.  This  fact  is  taken  advantage  of  for  the 
detection  of  acetic  acid. 

Experiment  19.  To  a  mixture  of  about  equal  parts  of  acetic  acid 
and  alcohol,  in  a  test-tube,  add  a  little  concentrated  sulphuric  acid,  and 
notice  the  odor.  It  is  that  of  ethyl  acetate  or  acetic  ether. 


ACETYL    CHLORIDE,  ETC.  61 

Acetic  anhydride  or  acetyl  oxide,  C4H6O3.  —  This  sub- 
stance, which  bears  to  acetic  acid  the  relation  of  an  anhydride, 
is  made  by  abstracting  water  from  the  acid. 

2  C2H402  =  C4H603  +  H20. 

Like  other  acids,  acetic  acid  contains  hydroxyl,  as  will  be 
shown  below.  We  may  hence  represent  the  acid  thus  : 
C2H3O.OH.  The  part  C2H3O  is  known  as  acet}'l.  Now  when 
water  is  abstracted  from  the  acid,  the  change  takes  place  as  rep- 
resented in  this  equation  :  — 


C2H3O.OHj  __  C2H3OJ0 
C2H3O.OH  j  "  C2H30  r 

Hence,  according  to  this,  acetic  anhydride  appears  as  the  oxide 
of  acetyl,  while  the  acid  itself  is  the  hydroxide. 

Acetic  anhydride  is  a  colorless  liquid  which  boils  at  138°. 
With  water  it  gives  acetic  acid. 

Acetyl  chloride,  C2H3OC1.  -\      Just     as     alcohol,     when 

Acetyl  bromide,  C2H3OBr.  >•  treated  with  phosphorus  tri- 

Acetyl  iodide,       C2H3OI.     3  chloride,  yields  a  chloride  of 

ethyl,  so  acetic  acid,  when  treated  with  the  same  reagent,  yields 

acetyl  chloride.     The  character  of  the  reaction  is  the  same  in 

both  cases.     It   consists   in  the  replacement  of  hydroxyl  by 

chlorine. 

3  C2H3O.OH  +  PC13  =  3  C2H3OC1  +  P(OH)3. 

Acetyl  chloride. 

Experiment  2O.  Arrange  a  dry  distilling  flask,  with  condenser  and 
<lry  receiver,  under  a  hood  or  out  of  doors.  Bring  together  9  parts 
(say  1808)  strong  acetic  acid  and  6  parts  (say  120^)  phosphorus  tri- 
chloride. Slightly  heat  the  mixture  on  the  water-bath,  when  acetyl 
chloride  will  distil  over.  Collect  in  a  dry  bottle. 

Acetyl  chloride  is  a  colorless  liquid  which  boils  at  55°. 
Water  acts  upon  it  very  readily,  acetic  and  hydrochloric  acids 
being  formed  :  — 

C2H3OC1  +  H20  =  C2H3O.OH  +  HC1. 


62  DEBIVATIVES   OF   METHANE   AND   ETHANE. 

In  this  case  the  chlorine  is  replaced  by  hydroxyl.  As  the  sub- 
stance is  volatile,  it  fumes  in  contact  with  the  air  in  consequence 
of  the  formation  of  hydrochloric  acid.  It  must  be  kept  in 
tightly-stoppered  bottles.  In  handling  it,  care  must  be  taken 
not  to  bring  it  near  the  nose,  as  its  odor  is  very  suffocating,  and 
it  attacks  the  mucous  membranes  of  the  eyes  and  nose,  produc- 
ing coughing  and  other  bad  results. 

Acetyl  chloride  is  a  valuable  reagent  much  used  in  the  exam- 
ination of  compounds  of  carbon.  Its  value  depends  upon  its 
action  towards  alcohols.  When  it  is  brought  together  with  an 
alcohol,  as,  for  example,  methyl  alcohol,  hydrochloric  acid  is 
evolved,  and  the  acetyl  group  takes  the  place  of  the  hydrogen 
of  the  alcoholic  hydroxyl :  — 

CH3.OH  +  C2H3OC1  =  CH3.O.C2H30  +  HCL 

The  product  is  an  ethereal  salt,  methyl  acetate.  This  kind  of 
action  takes  place  whenever  an  alcohol  is  treated  with  acetyl 
chloride.  Hence  if,  on  treating  a  substance  with  acetyl  chloride, 
its  composition  is  changed,  showing  that  hydrogen  is  replaced  by 
acetyl,  we  are  justified  in  concluding  that  the  substance  contains 
alcoholic  hydroxyl.  The  bromide  and  iodide  resemble  the 
chloride  very  closely. 

Experiment  21.  Treat  a  few  cubic  centimetres  of  absolute  alcohol 
with  acetyl  chloride.  Notice  the  evolution  of  hydrochloric  acid  and 
the  odor  of  ethyl  acetate. 

Substitution-products  of  acetic  acid.  These  bear  the  same 
relation  to  acetic  acid  that  the  substitution-products  of  marsh 
gas  bear  to  marsh  gas.  They  are  formed  by  the  simple  sub- 
stitution of  a  halogen,  etc.,  for  h3'drogen.  Only  three  of  the 
four  hydrogen  atoms  of  acetic  acid  are  capable  of  direct 
replacement.  The  fourth  is  the  one  to  which  the  acid  prop- 
erties are  due.  Hence  the  substitution-products  are  acid.  The 
best  known  of  these  products  are  the  chlor-acetic  acids  which 
are  made  by  treating  the  acid  with  chlorine.  They  are 


RELATIONS   BETWEEN   COMPOUNDS   OF   CARBON.       68 

mono  -chlor-  acetic,  di-chlor- acetic,  and  tri-clilor-  acetic  acids. 
Their  formation  is  represented  by  the  following  equations  :  — 

C2H3O.OH  +  C12  =  C2H2C10.0H  +  HC1 ; 
C2H2C1O.OH  +  C12  =  C2HC12O.OH  +  HC1 ; 
C2HC12O.OH  +  C12  =  C2C13O.OH  +  HC1. 

When  treated  with  nascent  hydrogen  they  are  converted 
back  into  acetic  acid.  They  yield  salts,  ethereal  salts,  anhy- 
drides, etc.,  just  the  same  as  acetic  acid  itself. 

Theory  in  regard  to  the  relations  between  the  acids,  alcohols, 
aldehydes,  and  hydrocarbons.  The  reactions  and  methods  of 
formation  of  acetic  acid  enable  us  to  form  a  clear  conception  in 
regard  to  the  relation  of  its  constituents.  In  the  first  place 
the  presence  of  hydroxyl  is  shown  by  the  reaction  with  phos- 
phorus trichloride.  We  hence  have  C2H3O.OH  as  the  formula 
representing  this  idea.  But  several  questions  still  remain  to  be 
answered.  There  is  another  oxygen  atom  to  be  accounted  for ; 
and  the  relations  between  the  hydroxyl  and  this  oxygen  must 
be  determined  if  possible.  The  fact  that  this  second  oxygen 
is  not  readily  replaced  by  chlorine  indicates  that  it  is  not 
present  as  hydroxyl,  and  all  methods  of  testing  for  hydroxyl 
fail  to  show  its  presence  in  acetyl  chloride.  Hence  we  may 
conclude  that  the  second  oxygen  atom  is  present  as  carbonyl 

O 

II 
CO.    This  leads  us  to  the  formula  H  —  C  —  O  —  H  for  the  simplest 

acid,  or  formic  acid.  Accordingly,  formic  acid  appears  as 
carbonic  acid,  which  we  commonly  represent  by  the  formula 

0  =  C  (       t  in  which  one  hydroxyl  has  been  reduced  to  hydrogen. 

We  have  already  seen  that  this  reduction  can  be  accomplished 
without  difficulty.  Many  other  arguments  might  be  brought 
forward  in  favor  of  the  view  that  the  above  formulas  express 
the  relations  between  formic  and  carbonic  acids.  Now,  as 
acetic  acid  is  the  homologue  of  formic  acid,  we  have  every 


64  DERIVATIVES   OF   METHANE  AND   ETHANE. 

reason  to  believe  that  it  differs  from  the  latter  in  that  it  con- 
tains methyl  in  place  of  the  hydrogen,  which  is  in  direct  com- 
bination with  carbon.      It  must  hence  be  represented  by  the 
O 

formula  CH3.C  — OH  or  CO  /  '    3.     The  common  constituent  of 

XOH 

0 

II 

the  two  acids,  is  the  group  C  — O  — H  or  —CO. OH,  which  is  gener- 
ally known  as  carboxyl.  Acetic  acid  is  closely  related  not  only 
to  formic  but  to  carbonic  acid.  It  may  be  regarded  as  carbonic 

acid,  CO  \       i  in  which  one  hydroxyl  is  replaced  by  the  radical 

OH 
methyl.     In  a  similar  way  we  shall  see  that  all  organic  acids 

may  be  regarded  as  derived  either  from  formic  acid  or  from 
carbonic  acid. 

Representing  now  the  simplest  hydrocarbon,  alcohol,  alde- 
hj'de,  and  acid,  by  the  structural  formulas  deduced  from  the 
facts,  we  have 

,  mi 

o  ro 

H  C^  OH. 

H  ^H 

Marsh  gas.  Methyl  alcohol.  nldehycfe.  Formic  acid. 

Concerning  the  mechanism  of  the  changes  caused  by  oxida- 
tion, but  little  can  be  determined  by  experiment.  We  may 
regard  methyl  alcohol  as  the  first  and  simplest  product  of 
oxidation  of  marsh  gas.  Starting  with  methyl  alcohol,  we 
might  expect  the  next  change  to  consist  in  the  introduction 

JOH 
OH.     But  it  ap- 


pears  to  be  a  law  that,  except  under  certain  peculiar  conditions, 
one  carbon  atom  cannot  hold  two  hydroxyls  in  combination, 


RELATIONS    BETWEEN   COMPOUNDS   OF   CARBON.        65 

and  that,  if  such  a  body  is  formed,  it  loses  the  elements  of 

{  OH 

JOH  fO 

water;   thus,  C  4  R    =  C     n+H20.      The  result  would  be  the 


2 
H 

aldehyde.     This  kind  of  change  is  illustrated  in  the  formation 
of  carbon  dioxide  from  the  salts  of  carbonic  acid.     Instead  of 

getting  the  acid  CO  <r)Tr5  which  we  would  naturally  expect,  we 
get  this  minus  water  :  — 


Now,  when  the  aldehyde  is  oxidized,  another  oxygen  atom  is 
introduced,  and  the  substance  thus  produced  is  an  acid,  or  the 
hydroxyl  hydrogen  can  be  replaced  by  metals,  and  has  in  general 
the  characteristics  of  acid  h}'drogen.  As  soon  as  we  have  car- 
bon in  combination  with  oxygen  as  carbon}-!,  and  also  with 
hydroxyl,  the  substance  containing  the  combination  is  an  acid. 

(° 
If,  finally,  the  acid  C  )  OH  be  oxidized,  it  is  probable  that  the 

(H 
same  change  takes  place  as  when  the  alcohol  is  oxidized.     That 

is  to  say,  the  hydrogen  is  probably  replaced  by  hydroxyl,  when 
a  compound  containing  two  hydroxyls  in  combination  with  one 
carbon  atom  would  be  the  result.  This  would  be  ordinary  car- 
bonic acid.  But  this  breaks  up  into  water  and  carbon  dioxide, 
which,  as  we  know,  are  the  products  of  oxidation  of  formic 
acid. 

All  the  many  representatives  of  the  great  classes  of  carbon 
compounds  known  as  the  alcohols,  aldehydes,  and  acids  are 
closely  related  to  the  three  fundamental  substances,  methyl 
alcohol,  formic  aldehyde,  and  formic  acid.  Replace  one  of 

the  hydrogen  atoms  of  methyl  alcohol  by  a  radical,  and  we  get  a 

,  OH 

TT 

new  alcohol,  which  may  be  represented  by  the  formula  C  j  -jj-  • 

1  R 
So  also  a  similar  replacement  of  a  hydrogen  atom  in  formic 


66  DEEIVATIVES    OF   METHANE   AND   ETHANE. 


f° 
,  C  4  H  ;  and, 

IB 


aldehyde  gives  another  aldehyde,  C-JH;  and,  finally,  as  we  have 

IB 

seen,  the  acids  of  carbon  may  be  represented  by  the  formulas 

c° 

C  )  OH,  or  R.CO.OH,  or  CO  <  R    ,  which  show  their  relations  to 

( R  OH 

formic  and  carbonic  acids.  Hereafter,  in  writing  the  formulas 
of  members  of  the  three  great  classes,  the  structure  will  be  repre- 
sented by  writing  the  hydroxyl  group  OH,  the  aldehyde  group 
CHO,  and  the  carboxyl  group  CO. OH  or  CO2H,  separately 
from  the  rest  of  the  formula. 

5.  ETHEREAL  SALTS  OR  COMPOUND  ETHERS. 

Whenever  an  acid  acts  upon  an  alcohol,  the  acid  is  neutralized 
either  wholly  or  partly,  and  a  product  analogous  to  the  salts  is 
formed.  Thus  nitric  acid  and  ethyl  alcohol  give  ethyl  nitrate  :  — 

C2H5.OH  +  HN03  =  C2H5.N03  4-  H2O, 

just  as  nitric  acid  and  potassium  hydroxide  give  potassium 
nitrate.  It  has  been  pointed  out  that  the  radicals,  methyl,  CH3, 
and  ethyl,  C2H5,  take  the  part  of  metals  in'  the  ethereal  salts. 
We  may  thus  get  a  series  of  methyl  and  ethyl  salts  with  the 
various  acids. 

As  regards  the  preparation  of  these  compounds,  it  should  be 
remarked  that  the  action  between  an  alcohol  and  an  acid  does 
not  take  place  as  readily  as  that  between  an  acid  and  a  metallic 
hydroxide.  Only  a  few  of  the  strongest  acids  act  directly 
without  aid.  Such,  for  example,  are  nitric  and  sulphuric  acids, 
though  even  the  latter  is  not  completely  neutralized  by  action 
upon  alcohols,  as  has  already  been  seen  in  the  preparation  of 

C  TT 

ethyl-sulphuric  acid,    2    °  >  SO4,  for  the  purpose  of  making  ether. 

Plainly  ethyl- sulphuric  acid  is  an  acid  ethereal  salt,  analogous 
to  acid  potassium  sulphate.  Both  are  still  acid,  though  both 
are  likewise  salts. 


ETHEREAL   SALTS.  67 

The  methods  which  may  be  used  for  preparing  ethereal  salts 
are  the  following  :  — 

(1)  Treatment  of  an  acid  with  an  alcohol.     This  is  capable 
of  only  very  limited  application,  as  in  the  case  of  a  few  of  the 
strongest  acids. 

(2)  Treatment  of  the  chloride  of  an  acid  with  alcohol.     This 
has  been  illustrated  by  the  action  of  acetyl  chloride,  C2H3O.C1, 
upon  methyl  alcohol  (see  p.  62)  :  — 

C2H3OC1      +  HO.CH3  =  C2H3O.OCH3    +  HC1, 
or          CH3.COC1  +  HO.CH3  =  CH3.COOCH3  +  HC1. 

(3)  Treatment  of  the  silver  salt  of  an  acid  with  a  halogen 
substitution  -product  of   a   hydrocarbon.      For   example,  ethyl 
acetate  may  be   made   by  treating    silver    acetate  with   brom- 
ethane  :  — 

CH3.COOAg  +  C2H5Br  =  CH3COOC2H5  +  AgBr. 

This  reaction  is  well  adapted  to  showing  the  relation  between 
the  salt  and  the  ethereal  salt,  and  leaves  no  room  for  doubt  that 
the  two  are  strictly  analogous. 

(4)  Treatment  of  a  mixture  of  an  alcohol  and  an  acid  with 
dry  hydrochloric  acid  gas  or  strong  sulphuric  acid.     The  forma- 
tion of  ethyl  acetate  by  this  method  was  illustrated  in  Experi- 
ment 19,  p.  60.     The  sulphuric  acid  facilitates  the  action  by 
uniting  with  the  alcohol  to  form  ethyl-sulphuric  acid,  which  with 
the'  acid  gives  the  ethereal  salt  :  — 


S04  +  CH3.COOH  =  CH3.COOC2H5  +  H2SO4. 
H 

The  action  of  the  hydrochloric  acid  is  not  understood.  It  is 
possible  that  it  acts  upon  the  acids  forming  the  chloride,  and 
that  this  then  acts  upon  the  alcohol,  forming  the  ethereal 
salt  :  — 

CHg.COOH  +  HC1         =  CH3.COC1         +  H2O  ; 
.  CH3.COC1    +  C2H5OH  =  CH3.COOC2H5  +  HC1. 


68  DERIVATIVES   OF   METHANE   AND   ETHANE. 

Among  the  more  important  ethereal  salts  of  methyl  and  ethyl 
alcohols,  the  following  may  be  mentioned  :  — 


Methyl-sulphuric    acid,       H3  >  SO4,  formed  by  mixing- 

methyl  alcohol  and  sulphuric  acid.  The  acid  itself,  as  well  as 
its  salts,  is  very  easily  soluble  in  water. 

Ethyl  nitrate,  C2H5NO3,  formed  by  treating  alcohol  with 
nitric  acid.  Unless  precautions  are  taken  in  mixing  these 
reagents,  complete  decomposition  of  the  alcohol  will  take  place, 
and  the  action  will  be  accompanied  by  a  violent  explosion. 

Ethyl-sulphuric  acid,  C^5  >  SO4-    Made  in  the  same  way 

±1 

as  the  methyl  compound.  The  acid  and  its  salts  are  easily  sol- 
uble in  water.  When  boiled  with  water  it  is  decomposed, 
yielding  alcohol  and  sulphuric  acid  :  — 


H 

Ethyl  sulphate,  (C2H5)2SO4,  is  made  by  passing  the  vapor 
of  sulphur  trioxide  into  well-cooled  ether  :  — 

(C2H5)20  +  S03  =  (C2H5)2S04. 

Phosphoric  acid  yields  ethyl  phosphate,  (C2H5)3PO4,  di-ethyl-phos- 
phoric  acid,  (C2H5)2HPO4,  and  ethyl-phosphoric  acid,  C2H5H2PO4. 

There  also  are  similar  derivatives  of  arsenic,  boric,  silicic,  and 
other  mineral  acids. 

Of  the  ethereal  salts  which  the  two  alcohols  form  with  formic 
and  acetic  acids,  methyl  and  ethyl  acetates  are  the  best  known. 
The  methods  of  preparing  them  have  already  been  considered. 
They  are  both  liquids  having  pleasant  odors.  This  is  indeed  a 
characteristic  of  many  of  the  volatile  ethereal  salts  of  the  acids 
of  carbon,  and  many  of  the  odors  of  fruits  and  flowers  are  due 
to  the  presence  of  one  or  another  of  these  compounds.  Many 


SAPONIFICATION.  69 

of  them  also  are  used  for  flavoring  purposes  instead  of  the 
natural  substances. 

Experiment  22.  Make  a  mixture  of  15  parts  (150s)  of  ordinary 
concentrated  sulphuric  acid  and  6  parts  (60s)  absolute  alcohol.  Add 
to  it  10  parts  (100§)  sodium  acetate.  Distil  from  a  flask.  Redistil 
the  distillate.  The  ethyl  acetate  thus  formed  boils  at  77°.  What 
reactions  take  place  in  this  case? 

Decomposition  of  ethereal  salts.  Salts  of  most  metals  are 
decomposed  when  treated  with  an  alkaline  hydroxide,  as  caustic 
soda  or  caustic  potash,  the  result  being  a  salt  of  the  alkali  and 
the  hydroxide  of  the  replaced  metal,  as  seen  in  the  case  of 
copper  sulphate  and  sodium  Ivydroxide  :  — 

CuSO4  +  2  NaOH  =  Cu(OH)2  +  Na2SO4. 

So  also  the  ethereal  salts  are  decomposed  when  treated  with  the 
alkalies,  though,  as  a  rule,  not  as  readily  as  salts.  It  is  usually 
necessary  to  boil  the  ethereal  salt  with  the  alkali  when  decom- 
position takes  place,  the  radical,  like  the  metal,  appearing  in 
the  form  of  the  hydroxide  or  alcohol,  and  the  alkali  metal  taking 
its  place.  Thus,  when  ethyl  sulphate  is  treated  with  a  solution 
of  caustic  potash,  this  reaction  takes  place  :  — 

(C2H5)2SO4  +  2  KOH  =  K2SO4  +  2  C2H5.OH ; 

and  when  ethyl  acetate  is  treated  with  caustic  soda,  we  have  this 
reaction :  — 

CH3.COOC2H5  +  NaOH  =  CH3.COONa  +  C2H5OH. 

Experiment  23.  In  a  500CC  flask  put  200CC  water,  50&  solid 
caustic  potash,  and  20CC  ethyl  acetate.  Connect  with  an  inverted  con- 
denser, arranged  as  shown  in  Fig.  8.  Boil  gently  for  half  an  hour. 
Now  connect  the  condenser  with  the  flask  for  distilling,  and  again  boil. 
Examine  the  distillate  for  alcohol.  Acidify  the  contents  of  the  flask 
with  sulphuric  acid,  and  again  distil.  What  passes  over? 

All  ethereal  salts  are  decomposed  by  boiling  with  the  caustic 
alkalies.  As  this  decomposition  is  best  known  on  the  large  scale 
in  the  preparation  of  soaps,  it  is  commonly  called  saponiftcation. 


70  DERIVATIVES    OF   METHANE   AND   ETHANE. 

As  will  be  shown,  the  fats  are  ethereal  salts,  and  soap-making 
consists  in  decomposing  these  fats  by  means  of  the  alkalies. 
Hence,  generally,  to  saponify  an  ethereal  salt  means  to  decom- 
pose it  by  means  of  an  alkali  into  the  corresponding  alcohol  and 
the  alkali  salt  of  the  acid  contained  in  it. 


Fig.  8. 

6.  KETONES  OR  ACETONES. 


When  an  acetate  is  distilled,  a  liquid  passes  over  which  has 
the  composition  C3H6O,  and  a  carbonate  remains  behind.  The 
reaction  has  been  carefully  studied,  and  has  been  shown  to  take 
place  in  accordance  with  the  following  equation  :  — 


The  substance  C3H6O  is  known  as  acetone.  It  is  the  best 
known  representative  of  a  class  of  bodies  which  are  sometimes 
called  acetones,  but  more  commonly  Jcetones. 

Acetone,  C3H6O.  —  This  substance  has  long  been  known  as 
a  product  of  the  distillation  of  acetates,  as  above  stated.  It  is 
contained  in  large  quantities  in  the  product  obtained  in  the 


ACETONE.  71 

distillation  of  wood,  and  may  be  separated  from  the  mixture 
after  the  removal  of  the  acetic  acid. 

It  may  be  purified  by  shaking  a  mixture  containing  it  with  a 
concentrated  solution  of  mono-sodium  sulphite.  It  unites  with 
the  salt,  forming  a  compound  analogous  to  that  formed  with 
aldehyde.  The  double  compound  may  be  separated,  and  when 
distilled  with  the  addition  of  potassium  carbonate  acetone  passes 
over. 

Acetone  is  a  colorless  liquid  having  a  penetrating  pleasant 
ethereal  odor.  It  boils  at  56.3°.  It  is  a  good  solvent  for  many 
carbon  compounds,  such  as  resins,  fats,  etc. 

On  studying  the  conduct  of  acetone,  it  soon  becomes  evident 
that  it  more  closely  resembles  the  aldehydes  than  any  other 
bodies  thus  far  considered.  It  is  plainly  not  an  acid  nor  an 
alcohol.  It  acts  entirely  differently  from  either.  It  is  not  an 
ethereal  salt,  for  on  boiling  with  an  alkali  it  does  not  yield  an 
alcohol  nor  the  salt  of  an  acid.  On  the  other  hand,  it  unites 
with  the  acid  sulphites  like  the  aldehydes.  Further,  when 
treated  with  phosphorus  pentachloride  its  oxygen  is  replaced  by 
two  chlorine  atoms  thus  :  — 

C3H60  +  PC15  =  C3H6C12  +  POC13; 

and  when  treated  with  nascent  hydrogen,  it  is  converted  into  a 
substance  having  alcoholic  properties.  These  facts  lead  us  to 
the  conclusion  that  the  substance  contains  carbonyl,  CO,  as  the 
aldehydes  do,  and  we  thus  have  the  formula,  C2H6CO.  The 
formation  from  calcium  acetate  leads  further  to  the  belief  that 
the  group  C2H6  really  consists  of  two  methyls,  as  the  simplest 
interpretation  of  the  reaction  is  represented  thus  :  — 

CH3COO     p         CH3     pO       Popo 
CH3COO>        -CH3>  A" 

According  to  this,  acetone  is  a  compound  of  two  methyl  groups 
and  carbonyl,  or  it  is  carbon  monoxide  whose  two  available 
affinities  have  been  satisfied  by  two  methyl  groups. 


72  DERIVATIVES    OF   METHANE   AND   ETHANE. 

We  may  test  the  correctness  of  this  view  by  means  of  synthe- 
ses. '  If  it  is  correct,  it  will  be  seen  that  acetone  is  closely 
related  to  acetyl  chloride.  It  is  acetyl  chloride  in  which  the 
chlorine  has  been  replaced  by  methyl :  — 

CH3.CO.C1  CH3.CO.CH3. 

Acetyl  chloride.  Acetone. 

Now,  when  acetyl  chloride  is  treated  with  zinc  methyl,  Zn(CH3)2, 
it  yields  acetone  according  to  this  equation  :  — 

2  CH3.COC1  +  Zn(CH3)2  =  2  CH3.CO.CH3  +  ZnCl2. 

Further,  acetone  may  be  made  by  treating  carbon  monoxide 
with  sodium  methyl,  a  direct  addition  of  two  methyl  groups  to 
carbon  monoxide  being  thus  effected.  The  relation  between 
acetone  and  ordinary  acetic  aldehyde  is  like  that  of  an  ethereal 
salt  to  its  acid ;  that  is,  acetone  is  aldehyde,  CH3.COH,  in 
which  the  hydrogen  has  been  replaced  by  methyl,  CH3.CO.CH3. 

Like  the  aldehydes,  the  acetone  has  the  power  of  taking  up 
other  substances,  such  as  the  acid  sulphites,  ammonia,  hydro- 
cyanic acid,  hydrogen,  etc.  This  power  is  in  some  way  con- 
nected with  the  relation  of  the  oxygen  to  the  carbon,  which  is 
the  same  in  both  compounds.  Nevertheless,  this  condition  of 
the  oxygen  does  not  always  carry  with  it  the  same  power  as 
seen  in  the  case  of  the  acids  which  also  contain  carbonyl. 

By  reduction  with  nascent  hydrogen,  acetone  yields  an  alco- 
hol of  the  formula  C3H8O,  known  as  secondary  propyl  alcohol, 
which  when  oxidized  yields  acetone.  In  other  words,  the  rela- 
tion between  this  alcohol  and  acetone  is  much  the  same  as  that 
between  ethyl  alcohol  and  acetic  aldehyde.  But  while  the  alde- 
hyde by  further  oxidation  yields  acetic  acid  by  simply  taking 
up  one  atom  of  oxj'gen,  acetone  is  decomposed  by  oxidizing 
agents,  and  yields  acetic  and  carbonic  acids.  Towards  oxidiz- 
ing agents,  then,  acetones  (for  it  will  be  shown  that  other 
acetones  conduct  themselves  in  the  same  way)  act  entirely 
differently  from  the  aldehydes.  The  alcohol  above  mentioned 


GENERAL    STATEMENTS.  73 

as  related  to  acetone  is  the  simplest  representative  of  a  class  of 
alcohols  differing  in  some  respects  from  the  substances  com- 
monly called  alcohols. 


We  have  thus  considered  the  most  important  representatives 
of  six  classes  of  oxygen  derivatives  of  the  hydrocarbons,  and, 
by  a  study  of  their  chemical  conduct  and  the  methods  available 
for  their  preparation,  have  formed  views  in  regard  to  the  rela- 
tions between  them.  In  our  ordinary  language  we  may  express 
these  relations  briefly  thus :  The  alcohols  are  the  hydroxyl 
derivatives  of  the  hydrocarbons  or  the  hydroxides  of  certain 
groups  called  radicals;  the  ethers  are  the  oxides  of  these  same 
radicals  ;  the  aldehydes  are  compounds  consisting  of  carbonyl, 
hydrogen,  and  a  radical ;  the  acids  are  compounds  of  carbonyl, 
hydroxyl,  and  a  radical,  or,  better,  they  are  carbonic  acid  in 
which  hydrogen  and  oxygen,  or  hydroxyl,  have  been  replaced 
by  a  radical ;  the  ethereal  salts  are  compounds  like  ordinary 
metallic  salts,  only  they  contain  a  radical  in  the  place  of  the 
metal ;  and,  finally,  the  ketones  are  aldehydes  in  which  the 
distinctively  aldehyde  hydrogen  has  been  replaced  by  a  radical, 
or  they  are  compounds  consisting  of  carbonyl  and  two  radicals. 

These  ideas  are  expressed  in  formulas  thus,  R  being  any 
univalent  radical  like  methyl,  CH3,  or  ethyl,  C2H5 :  — 

Alcohol     ....     R-O-H. 
Ether R-O-R. 

Aldehyde  ....     R-C-H. 

I! 

o 

Acid R-C-O-H. 

II 

O 

Ethereal  salt       .     .     Ac— O  — R  (in  which  Ac  — O— H  repre- 
sents any  monobasic  acid). 
Ketone  R-C-R. 


76  DERIVATIVES   OF   METHANE   AND   ETHANE. 

3.  SULPHONIC  ACIDS. 

It  was  stated  above,  that  when  mercaptan  is  oxidized  it  is 
converted  into  an  acid  of  the  formula  C2H5.SO3H,  or  ethyl-sul- 
phonic  acid.  This  is  the  representative  of  a  large  class  of  sub- 
stances which  are  commonly  made  by  treating  carbon  compounds 
with  sulphuric  acid.  These  sulphonic  acids  can  best  be  studied 
in  connection  with  another  series  of  hydrocarbons.  Under  the 
head  of  Benzene  (which  see)  it  will  be  shown  that,  when  this 
hydrocarbon  is  treated  with  sulphuric  acid,  a  reaction  takes 
place  which  may  be  represented  thus  :  — 


C6H6  +         >  S02  =          >  S02  +  H20. 

Benzene.  Benzene-sulphonic  acid. 

The  sulphonic  acid  thus  obtained  may  also  be  made  by  oxi- 
dizing the  corresponding  mercaptan  or  hydrosulphide,  C6H5.  SH. 
Accordingly,  the  sulphonic  acid  appears  to  be  sulphuric  acid  in 
which  a  hydroxyl  has  been  replaced  by  the  radical  C6H5.  Rea- 
soning by  analogy,  which,  fortunately,  is  supported  by  other 
arguments,  we  may  conclude  that  ethyl-sulphonic  acid  formed 
from  ethyl-mercaptan  bears  a  similar  relation  to  sulphuric  acid, 

r\  TT 

and  corresponds  to  the  formula    *   5  >  S02.     So,  also,  methyl- 
sulphonic    acid    obtained    by   oxidation   of    methyl-mercaptan 

O1T 
should  be  represented  by  the  formula        3>S02  or  CH3.SO2CH. 

Its  relation  to  sulphuric  acid  is  the  same  as  that  of  acetic  acid  to 
carbonic  acid. 

Another  method  by  which  the  sulphonic  acids  may  be  prepared 
consists  in  treating  a  sulphite  with  a  halogen  substitution-product. 
Thus  ethyl-sulphonic  acid  may  be  prepared  from  potassium  sul- 
phite and  iodo-ethane  :  — 


C2H5I  +         >  S03  =  >  S03  +  KI, 


C*  TT  T      L        •*•*'  "^  C/^              ^2AX5  ^  Qpi  T^T 

Or  i^S^JL    T    ^^  >  ^2    =       >  OU2    +   JM« 

KO 


STJLPHONIC   ACIDS.  77 

According  to  this  reaction  the  sulphonic  acids  would  appear  to 
be  identical  with  the  ethereal  salts  of  sulphurous  acid,  but  they 
do  not  conduct  themselves  like  ethereal  salts.  The  difference 
is  particularly  noticeable  in  connection  with  the  stability,  the 
sulphonic  acids  as  a  class  being  much  more  stable  than  the 
ethereal  salts  as  a  class.  At  present  it  would  be  somewhat 
premature  to  discuss  fully  the  question  as  to  their  relations. 
Whatever  we  may  call  them,  they  are  closely  related  to  sulphu- 
rous acid,  and  are  derived  from  it  by  replacement  of  hydro- 
gen by  a  radical,  just  as  acetic  acid  may  be  regarded  as  derived 
from  formic  acid  by  replacement  of  hydrogen  by  a  radical. 
These  relations  may  be  represented  by  the  following  form- 
ulas :  — 

OT-T  OTT 

Carbonic  acid,  CO  < ;™.       Sulphuric  acid,  SO2  <        . 

OH  OH 

TT  TT 

Formic  acid,     CO  <        .       Sulphurous  acid,  SO2  < 

OH  OH 

PTT  PIT 

Acetic  acid,      CO  <  ^fs.      Methyl-sulphonic  acid ,  SO2  <  ~**s. 
OH  OH 

Any  carbonic  j  CQ  <  B  A      Bnl  ^  ^       ^  <  E 

acid,  OH  OH 

The  difference  between  a  sulphonic  acid  and  an  ethereal  salt  of 
sulphuric  acid  should  be  specially  noticed.  Compare  for  this 

C*  TT  O 

purpose  ethyl-sulphuric  acid,     2  JL  >  S02,  and  ethyl-sulphonic 

C^  TT 

acid,     2   3  >  S02.     Both  are  monobasic  acids,  and  both  contain 
HO 

ethyl,  but  there  is  a  difference  of  one  atom  of  oxygen  in  their 
composition.  The  reactions  of  the  substances  are  such  as  to 
lead  to  the  conclusion  that  in  ethyl-sulphonic  acid  the  ethyl 
group  is  directly  connected  with  the  sulphur ;  whereas,  that  in 
ethyl-sulphuric  acid  the  connection  is  established  by  means  of 
oxygen.  The  strongest  argument  in  favor  of  this  view  is 
perhaps  that  which  is  founded  on  the  formation  of  the  sulphonic 
acids  by  oxidation  of  the  hydrosulphides  or  mercaptans.  It 


78  DERIVATIVES    OF   METHANE    AND    ETHANE. 

can  hardly  be  doubted  that  in  ethyl  mercaptan  the  sulphur  is  in 
direct  combination  with  the  ethyl ;  or,  to  go  still  farther,  that 
it  is  in  combination  with  carbon  as  represented  in  the  formula 

H 
H3C  — C  — S  — H.     Now,  by  oxidation  of  mercaptan,  three  atoms 

H 

of  oxygen  are  added,  and  the  simplest  view  we  can  take  of  the 
reaction  is  that  the  sulphur  is  left  undisturbed  in  its  relations  to 
ethyl,  but  that  it  has  taken  up  the  oxygen,  as  represented  in  the 
formula  C2H6  — SO2.OH.  As  has  been  shown,  the  oxygen  can 
be  removed  again  by  nascent  hydrogen,  and  the  result  is  mer- 
captan. The  study  of  the  sulphonic  acids  in  their  relations  to 
sulphuric  and  sulphurous  acids  has  been  of  considerable  assist- 
ance in  enabling  chemists  to  form  conceptions  in  regard  to  the 
relations  of  the  constituents  of  the  two  latter.  The  view  which 
is  forced  upon  us  by  a  consideration  of  the  reactions  described 
above  is  that  sulphurous  acid  differs  from  sulphuric  acid  in 
containing  a  hydrogen  atom  in  place  of  Irydroxyl,  as  represented 

OTT  IT 

in  the  formulas  SO2  <         and  S02  <        ;  and,  further,   that  in 

sulphurous  acid  one  hydrogen  is  in  combination  with  sulphur 
and  the  other  with  oxygen. 


CHAPTER   VI. 

NITROGEN  DERIVATIVES  OP   METHANE  AND 
ETHANE. 

THE  simplest  compounds  of  carbon  containing  nitrogen  are 
cyanogen  and  hydrocyanic  acid.  Strictly  speaking,  neither  can 
be  regarded  as  a  derivative  of  a  hydrocarbon,  unless  indeed  we 
consider  hydrocyanic  acid  as  marsh  gas,  in  which  three  hydro- 

(H 

TT 

gen   atoms  have   been  replaced   by  one  nitrogen :   C  4        and 

\  H 

C  <     •     That,  however,  is  a  mere  matter  of  words,  as  there  is 
(  H 

nothing  in  the  conduct  of  either  substance,  or  in  the  methods  of 
formation  of  hydrocyanic  acid,  that  would  lead  us  to  suspect 
any  relation  between  them.  Though  cyanogen  and  hydrocyanic 
acid  are  therefore  not  to  be  considered  as  derivatives  of  the 
hydrocarbons,  they  form  the  starting-point  for  the  preparation 
of  so  many  important  compounds  that  they  and  their  simpler 
derivatives  must  receive  some  consideration  at  this  stage. 

Cyanogen,  (CN)2.  —  All  organic  compounds  which  contain 
nitrogen  give  sodium  cyanide  when  ignited  with  sodium.  So, 
also,  potassium  c}Tauide  is  formed  when  charcoal  containing 
nitrogen  is  heated  with  potassium  carbonate.  Cyanogen  itself 
is  most  readily  made  by  heating  mercuric  cyanide,  Hg(CN)2. 
The  decomposition  which  takes  place  is,  in  the  main,  like  the 
simple  decomposition  of  mercuric  oxide  in  preparing  oxygen  :  — 

Hg(CN)2=  Hg  +  (CN)2; 
HgO          =  Hg  +  O. 


80  DERIVATIVES   OF  METHANE   AND  ETHANE. 

But,  in  heating  mercuric  cyanide,  a  black  solid  substance,  para- 
cyanogen,  is  formed,  and  remains  behind  in  the  retort.  It  has 
the  same  composition  as  cyanogen,  and  is  therefore  a  polymeric 
modification. 

Cyanogen  (from  KiWos,  blue)  owes  its  name  to  the  fact  that 
several  of  its  compounds  have  a  blue  color.  It  is  a  colorless 
gas,  which  is  easily  soluble  in  water  and  alcohol,  and  is  ex- 
tremely poisonous.  It  burns  with  a  purple-colored  flame. 

In  aqueous  solution,  cyanogen  soon  undergoes  change,  and  a 
brown  amorphous  body  is  deposited.  In  the  solution  are  found 
hydrocyanic  acid,  oxalic  acid,  ammonia,  and  carbon  dioxide. 
A  little  dilute  acid  prevents  this  decomposition. 

Hydrocyanic  acid,  HON.  —  This  acid,  which  is  com- 
monly known  by  the  name  of  prussic  acid,  occurs  in  nature 
in  amygdalin,  in  combination  with  other  substances,  in  bitter 
almonds,  the  leaves  of  the  cheriy,  laurel,  etc.  It  is  prepared 
by  decomposing  metallic  cyanides  with  hydrochloric  acid,  as 
represented  in  the  equation :  — 

KCN  +  HC1  =  KC1  +  HCN. 

It  may  also  be  made  by  treating  chloroform  with  ammonia :  — 

CHC13  +  NH3     =  HCN        +  3  HC1, 
or  CHC13  +  5  NH3  =  NH4.CN  +  3  NH4C1. 

It  is  a  volatile  liquid,  boiling  at  26.5°,  which  solidifies  at  —  15°. 
It  has  a  very  characteristic  odor,  suggesting  bitter  almonds.  It 
is  extremely  poisonous.  It  dissolves  in  water  in  all  proportions, 
and  it  is  such  a  solution  which  is  known  as  prussic  acid.  Pure 
hydrocyanic  acid  is  very  unstable.  By  standing,  a  brown  sub- 
stance is  deposited.  By  boiling  with  alkalies  or  acids,  it  is 
converted  into  formic  acid  and  ammonia  (see  p.  56). 

Hydrocyanic  acid  may  be  detected  by  the  fact  that  when  its 
solution  is  saturated  with  caustic  potash,  and  a  solution  contain- 
ing a  ferrous  and  a  ferric  salt  added,  a  precipitate  of  Prussian 


POTASSIUM   FERROCYANIDE.  81 

blue  is  formed ;  or,  by  adding  yellow  ammonium  sulphide  to  its 
solution,  evaporating  off  the  excess  of  ammonium  sulphide,  and 
then  adding  a  drop  of  solution  of  ferric  chloride.  If  hydrocy- 
anic acid  was  present,  the  solution  turns  a  deep  blood  red. 

Cyanides.  —  Hydrocyanic,  like  hydrochloric  acid,  forms  a 
series  of  salts.  They  are  called  the  cyanides.  The  cyanides  of 
the  alkali  metals  and  of  mercury  are  soluble  in  water.  The 
cyanides  of  the  heavy  metals  have  a  marked  tendency  to  form 
double  cyanides,  and  those  double  cyanides  which  contain  an 
alkali  metal  are  soluble  in  water.  Hence,  the  precipitates 
formed  by  potassium  cyanide,  in  solutions  containing  the  heavy 
metals,  are  dissolved  by  excess  of  the  cyanide. 

Among  the  best  known  double  cyanides  are  the  two  salts, 
potassium  ferrocyanide  and  potassium  ferricyanide.  The  former 
is  commonly  known  as  yellow  prussiate  of  potash,  and  the  latter 
as  red  prussiate  of  potash. 

Potassium  ferrocyanide,  4  KCN.Fe(CN)2  +  3  H2O.  - 
This  salt  is  made  on  the  large  scale  by  melting  together,  in  iron 
vessels,  refuse  animal  substances  (i.e.,  organic  matter  contain- 
ing nitrogen)  with  potassium  carbonate  and  iron.  The  mass  is 
treated  with  water,  and  the  salt  which  is  thus  extracted  puri- 
fied by  crystallization. 

It  crystallizes  in  large  3'ellow  cr}<stals,  and  is  soluble  in  about 
four  parts  of  water  at  15°. 

When  ignited,  it  breaks  up  according  to  this  equation  :  — 

4  KCN.Fe(CN)2  ==  4  KCN  +  FeC2  +  N2. 

This  decomposition  is  made  use  of  for  the  purpose  of  preparing 
potassium  cyanide.  As,  however,  a  portion  of  the  cyanogen  is 
lost  in  this  wa}',  potassium  carbonate  is  generally  added,  when 
the  reaction  represented  by  the  following  equation  takes 
place :  — 

4  KCN.Fe(CN)2  +  K2CO3  =  5  KCN  +  KCNO  +  CO3  +  Fe, 


82  DERIVATIVES   OF   METHANE   AND   ETHANE. 

The  potassium  cyanide  made  in  this  way  always  necessarily  con- 
tains potassium  cyanate,  KCNO. 

Experiment  24.1  Make  a  mixture  of  8  parts  (160&)  dehydrated 
potassium  ferrocyanide  and  3  parts  (60s)  dry  potassium  carbonate. 
Fuse  in  an  iron  crucible,  at  a  low  red  heat,  until  a  specimen  taken 
out  and  placed  on  a  stone  is  white  when  solid.  Then  pour  out  on  a 
flat,  smooth  stone,  and  afterwards  break  up  and  put  in  a  dry  bottle. 

When  treated  with  dilute  sulphuric  acid,  the  ferrocyanide 
yields  hydrocyanic  acid  thus :  — 

2  [4  KCN.Fe(CN)2]  +  3  H2SO4 

=  6HCN  +  2[KCN.Fe(CN)2]  +  3  K2SO4. 

This  reaction  is  the  one  actually  made  use  of  for  the  prepara- 
tion of  hydrocyanic  acid. 

Potassium  ferrocyanide  is  the  starting-point  for  the  prepara- 
tion of  all  compounds  containing  c}Tanogen. 

Potassium  ferricyanide,  3  KCN.Pe(CN)3. — This  salt, 
known  as  red  prussiate  of  potash,  is  prepared  by  oxidizing  tlie 
ferrocyanide:  The  oxidation  is  effected  most  readily  by  means 
of  chlorine. 

Experiment  25.  Pass  chlorine  into  a  solution  of  potassium  ferro- 
cyanide until  the  solution  ceases  to  give  a  precipitate  with  ferric  chlo- 
ride. Then  evaporate  to  crystallization. 

Other  oxidizing  agents,  such  as  bromine,  potassium  perman- 
ganate, lead  peroxide,  etc.,  effect  the  same  transformation. 
The  essential  part  of  the  change  is  that  of  the  ferrous  cyanide, 
Fe(CN)2,  in  the  ferrocyanide,  to  ferric  cyanide,  Fe(CN)3,  which 
is  in  the  ferricyanide.  Potassium  ferricyanide  is  easily  soluble 
in  water,  and  crystallizes  from  its  concentrated  solutions  in 
large,  dark-red  crystals  belonging  to  the  rhombic  S3Tstem. 

In    alkaline    solutions    it    is    an    excellent    oxidizing   agent. 

1  Experiments  24  and  26  may  be  postponed  until  urea  is  considered,  when  they  may 
be  combined  with  the  artificial  preparation  of  urea. 


CYANIC    ACID.  83 

Reducing    agents,    such   as    hydrogen    sulphide,    sodium    thio- 
sulphate  (hyposulphite),  etc.,  convert  it  into  the  yellow  salt. 

Prussian  blue,  TurribuWs  blue,  soluble  Prussian  blue,  and 
Berlin  green  are  complex  cyanides  of  iron  represented  by  the 

formulas 

4Fe(CN)3.3Fe(CN)2, 

3Fe(CN)2.2Fe(CN)3, 
KCN .  Fe(CN)3 .  Fe(CN)2, 
and  Fe3  (CN)  8  -f  4  H2O ,  respectively. 

For  a  full  account  of  the  many  compounds  of  the  metals  and 
cyanogen,  the  student  is  referred  to  larger  works. 

Cyanogen  chlorides.— When  chlorine  is  allowed  to  act 
upon  C3~anides  or  dilute  hydrocyanic  acid,  a  volatile  liquid  is 
formed  which  has  the  composition  represented  by  the  formula 
CNC1.  It  boils  at  15.5°,  and  its  vapor  acts  upon  the  eyes, 
causing  tears.  It  is  known  as  liquid  cyanogen  chloride  to  dis- 
tinguish it  from  solid  cyanogen  chloride.  The  latter  has  the 
formula  (CN)3C13,  and  is  formed  by  treating  anhydrous  hydro- 
cyanic acid  with  chlorine  in  direct  sunlight.  The  liquid  variety 
is  partially  transformed  into  the  solid  when  kept  in  sealed 
tubes. 

Similar  compounds  of  cyanogen  with  bromine  and  iodine  are 
known. 

Cyanic  acid,  CONH.  —  When  a  cyanide  of  an  alkali  is 
treated  with  an  oxidizing  agent,  it  takes  up  oxygen  and  is  con- 
verted into  a  cyanate  :  — 

CNK  +  0  =  CONK. 

Experiment  26.1  Heat  a  mixture  of  8  parts  (160s)  dehydrated 
potassium  ferrocyanide,  and  3  parts  (60 z)  dry  potassium  carbonate  in  an 
iron  crucible.  When  the  transformation  into  the  cyanide  is  complete 
(see  Ex.  24,  p.  82),  take  the  crucible  out  of  the  furnace;  and,  after  it 

See  Note,  p.  82. 


84  DERIVATIVES   OF   METHANE   AND   ETHANE. 

has  cooled  down  somewhat,  but  while  the  mass  is  still  liquid,  add 
gradually  15  parts  (300s)  red  lead,  stirring  during  the  operation.  Put 
the  crucible  again  in  the  furnace  for  a  little  while ;  allow  the  reduced 
lead  to  settle,  and  then  pour  out  the  contents  on  a  smooth  stone.  After 
the  mass  is  cold,  break  up  and  extract  the  cyanate  with  alcohol  (of  86 
per  cent). 

Cyanic  acid  cannot  be  separated  from  its  salts,  as  it  breaks 
up  with  water  into  ammonia  and  carbon  dioxide  :  — 

CONH  +  H20  =  NH3  +  C02. 

The  potassium  salt  is  easily  soluble  in  water,  but  is  easily 
decomposed  by  it,  yielding  ammonia  and  potassium  carbon- 
ate :  — 

CONK  +  2  H2O  =  KHCO3  +  NH3. 

The  most  interesting  salt  of  cyanic  acid  is  ammonium  cyanate, 
CON.NH4.  It  may  be  made  by  adding  ammonium  sulphate  to 
a  solution  of  the  potassium  salt.  It  is  easily  soluble  in  water ; 
but,  if  allowed  to  stand  in  solution,  or  if  its  solution  be  heated, 
it  is  completely  transformed  into  urea,  which  is  isomeric  with  it. 
The  interest  connected  with  this  transformation  was  referred  to 
in  the  introductory  chapter  (p.  1).  It  will  be  considered  more 
fully  under  the  head  of  urea. 

Cyanuric  acid,  C3N3H3O3.  —  This  acid  bears  a  relation  to 
cyanic  acid  similar  to  that  which  solid  cyanogen  chloride, 
(CN)8C13,  bears  to  the  liquid  variety.  It  is  made  by  treating 
the  solid  chloride  with  water,  and  also  by  heating  urea.  It  is 
a  crystallized  substance. 

Sulpho-cyanic  acid,  CNSH.— Just  as  the  cyanides  of  the 
alkalies  take  up  ox}'gen  and  are  converted  into  cyauates,  so  also 
they  take  up  sulphur  and  are  converted  into  sulpho-cyanates  :  — 

CNK  +  S  =  CNSK. 

Potassium 
sulpho-cyanate. 


SULPHO-CYANIC    ACID.  85 

Experiment  27.  Melt  together  in  an  iron  crucible  17  parts  (85s) 
dry  potassium  carbonate  and  32  parts  (160*)  sulphur,  and  then  add  46 
parts  (230s)  powdered  dehydrated  potassium  ferrocyanide.  Keep  the 
mass  at  a  low  red  heat  until  the  ferrocyanide  is  destroyed.  After 
cooling,  extract  with  water,  neutralize  the  filtered  solution  with  sul- 
phuric acid,  evaporate,  and  separate  from  potassium  sulphate  by  means 
of  alcohol. 

Potassium  sulpho-cyanate  crystallizes  in  long  striated  prisms 
without  water  of  crystallization.  It  is  deliquescent.  When 
dissolved  in  water  the  temperature  sinks  markedly.  When  100 
parts  of  water  of  10.8°  are  mixed  with  150  parts  of  the  salt,  the 
temperature  sinks  to  —  23.7°.  By  evaporation  of  the  solution, 
the  salt  can  be  recovered. 

Experiment  28.  Dissolve  some  potassium  sulpho-cyanate  in  water, 
and  note  the  temperature  before  and  after  introducing  the  salt. 

Ammonium  sulpho-cyanate,  CNS.NH4.  This  salt  is  most 
easily  prepared  by  treating  carbon  bisulphide  with  a  solution  of 
ammonia  in  dilute  alcohol :  — 

CS2  +  4  NH3  =  CNS.NH4  +  (NH4)2S. 

Experiment  29.  Mix  240CC  strong  aqueous  ammonia,  240CC  alcohol, 
and  60s  carbon  bisulphide.  Allow  the  mixture  to  stand  for  one  or 
more  days.  Then  distil  down  to  one-third  of  the  original  volume,  and 
filter  while  still  hot  the  solution  left  in  the  flask.  On  cooling,  ammo- 
nium sulpho-cyanate  will  crystallize  out. 

The  salt  crystallizes  in  plates.  It  melts  at  147°  (try  it), 
and  at  170°  it  is  transformed  into  the  isomeric  substance  known 
as  sulpho-urea.  (Analogy  to  transformation  of  ammonium 
cyanate.) 

Having  thus  considered  some  of  the  more  important  simpler 
cyanogen  compounds,  we  may  now  return  to  the  nitrogen  deriv- 
atives of  the  hydrocarbons.  For  convenience,  these  may  be 
divided  into  three  classes  :  — 

(1)  Those  which  are  related  to  cyanogen; 

(2)  Those  which  are  related  to  ammonia; 

(3)  Those  which  are  related  to  nitric  acid. 


86  DERIVATIVES   OF   METHANE   AND   ETHANE. 

CYANIDES. 

Methyl  cyanide,  CH3.CN.  — This  compound  is  formed  by 
distilling  a  mixture  of  potassium  methyl-sulphate  and  potas- 
sium cyanide' :  — 

CH3>S04  +  KCN  =  K2SO4  +  CH3CN. 
K 

It  is  a  liquid  boiling  at  82°. 

According  to  the  method  of  preparation,  it  must  be  regarded 
as  an  ethereal  salt  of  hydrocyanic  acid,  containing  methyl  in  the 
place  of  the  potassium  of  the  potassium  salt. 

Ethyl  cyanide,  C2H5.CN.  —  Formed  like  the  methyl  com- 
pound. Also  by  heating  chlor-ethane  with  potassium  cya- 
nide :  — 

C2H5C1  +  KCN  =  C2H5.CN  +  KC1. 

It  is  a  liquid  boiling  at  98°. 

The  two  most  characteristic  reactions  of  these  cyanides  are 
(1)  that  which  is  effected  by  caustic  alkalies,  and  (2)  that 
effected  by  nascent  hydrogen. 

When  methyl  cyanide  is  treated  with  caustic  potash,  it  yields 
acetic  acid  and  ammonia  :  — 

CH3.CN  +  H2O  +  KOH  =  CH3.CO2K  +  NH3. 

This  reaction  is  strictly  analogous  to  that  which  takes  place 
with  hydrocyanic  acid  yielding  formic  acid  (see  p.  56).  In 
the  same  way  ethyl  cyanide  yields  an  acid  of  the  formula 
C3H6O2  (or  C2H5.CO2H).  Thus,  by  making  a  cyanide,  we  have 
it  in  our  power  to  make  an  acid  containing  the  same  number  of 
carbon  atoms. 

This  reaction,  therefore,  enables  us  to  pass  from  an  alcohol 
to  an  acid  containing  one  atom  of  carbon  more  than  the  alcohol 
contains.  It  has  been  of  great  service  in  the  study  of  the  com- 
pounds of  carbon. 


ETHYL   CYANIDE.  87 

NOTE  FOR  STUDENT.  —  Show  how,  by  starting  with  methyl-alcohol, 
acetic  acid  may  be  made  by  passing  through  the  cyanide. 

There  are  two  ways  in  which  we  may  consider  the  cyanogen 
group  linked  to  methyl  in  methyl  cyanide;  viz.,  either  by  the 
carbon  atom,  as  represented  in  the  formula  H3C  — C^-N,  or 
by  the  nitrogen  atom,  as  represented  thus,  H3C— N— C.  The 
ease  with  which  the  nitrogen  is  separated  from  the  compound, 
leaving  the  two  carbon  atoms  together,  as  shown  in  the  reaction 
with  caustic  potash,  naturally  leads  to  the  conclusion  that  the 
former  view  is  the  correct  one.  If  it  is  correct,  it  would  appear 
to  follow  that  in  potassium  cyanide  the  potassium  is  in  combi- 
nation with  carbon  as  represented  in  the  formula  K— C— N, 
and  further  that  in  hydrocyanic  acid  the  hydrogen  is  in  combi- 
nation with  carbon,  as  shown  thus,  H  — C— N. 

In  consequence  of  the  close  relation  existing  between  the 
cyanides  and  the  acids,  the  former  are  frequently  spoken  of  as 
the  nitriles  of  the  acids.  Thus  methyl  cyanide,  which  is  con- 
verted into  acetic  acid  by  boiling  with  caustic  potash,  is  called 
the  nitrile  of  acetic  acid,  or  aceto-nitrile.  In  the  same  way 
hydrocyanic  acid  itself  ma}'  be  regarded  as  the  nitrile  of  formic 
acid,  or  formo-nitrile. 

When  methyl  cyanide  is  treated  with  nascent  hydrogen,  it  is 
converted  into  a  substance  which  closely  resembles  ammonia, 
and  is  known  as  ethyl-amine.  It  will  be  shown  to  bear  to 

(C2H5 
ammonia  the  relation  indicated  by  the  formula  N )  H     ;  i.e.,  it 

(H 
is  ammonia  in  which  one  hydrogen  has  been  replaced  by  ethyl. 

The  reaction  may  be  represented  by  the  equation  :  — 


H3C-C-N  +  4H  =  H3C-H2C-NH 


This  transformation  strengthens  the  conclusion  already  reached, 
that  the  two  carbon  atoms  in  methyl  cyanide  are  directly  united. 
If  this  were  not  the  case,  it  is  difficult  to  see  how  a  compound 


88  DERIVATIVES   OF  METHANE   AND   ETHANE. 

containing  ethyl  in  which  the  two  carbon  atoms  are  unquestion- 
ably united,  could  be  formed  so  easily  from  it. 

Just  as  methyl  cyanide  yields  ethyl-amine  when  treated  with 
nascent  hydrogen,    so   hydrocyanic   acid   yields   methyl-amine 

(CH3 
N)  H     :  — 

hi  / 

H-C-N  +  4H  =  H3C-NH2    or  N  4 


The  amines,  or  substituted  ammonias,  will  be  considered  more 
fully  hereafter. 

ISOCYANIDES    OR    CARBAMINES. 

If,  in  making  an  ethereal  salt  of  hydrocyanic  acid  from  a  salt, 
the  silver  salt  be  used,  a  compound  is  obtained  having  the  same 
composition  as  the  cyanide,  but  differing  very  markedly  from 
it.  The  substance  thus  obtained  is  called  an  isocyanide  or  car- 
bamine. 

Ethyl  isocyanide  or  ethyl  carbamine,  C2H5.NC.—  This 
compound  is  obtained  when  silver  cyanide  and  iodo-ethane  are 
heated  together  :  — 

C2H5I  +  AgNC  =  C2H5NC  +  Agl. 

It  is  also  formed  when  chloroform  and  ethyl-amine  (see  above) 
are  brought  together  :  — 

(C2H5 
CHC13  +  N    H      =  C2H5NC  +  3  HC1. 


It  is  a  liquid  boiling  at  79°.  It  is  characterized  by  an  unbear- 
able, indescribable  odor.  The  methyl  compound  obtained  by 
the  same  method  boils  at  58°  to  59°,  but  otherwise  has  proper- 
ties almost  identical  with  those  of  ethyl  isocyanide. 


ETHYL   ISOCYANIDE.  89 

The  reactions  of  these  substances  are  quite  different  from 
those  of  the  cyanides.  They  are  decomposed  only  with  great 
difficulty  b}r  the  caustic  alkalies  ;  but,  when  brought  together 
with  hydrochloric  acid,  the}'  undergo  an  interesting  change, 
which  may  be  represented  by  the  following  equation  for  the 
methyl  compound :  — 

CH3.NC  +  2H20  =  CH3-NH2  +  H.CO2H. 

Methyl-amine.  Formic  acid. 

This  reaction  indicates  that  in  the  isocyanides  the  cyanogen 
group  is  united  to  the  radical  by  means  of  nitrogen,  as  repre- 
sented by  the  formula  H3C— N— C.  Hence  it  is,  in  all  proba- 
bility, that  when  they  undergo  decomposition  the  nitrogen 
remains  in  combination  with  the  radical,  while  the  carbon  of 
the  cyanogen  group  passes  out  of  the  compound.  The  conduct 
of  ethyl  isocyanide  is  represented  by  the  equation  :  — 

C2H5.NC  +  2H2O  =  C2H5-NH2  -f  H.CO2H. 

The  reactions  of  the  cyanides  and  of  the  isoc^yanides,  and 
the  conclusions  drawn  from  them,  admirably  illustrate  the 
methods  used  in  determining  the  structure  of  compounds  of 
carbon ;  and  they  are  special!}*  valuable,  as  the  connection 
between  the  facts  and  the  conclusions,  as  expressed  in  the 
formulas,  can  be  traced  so  clearly. 

The  fact,  that  the  silver  salt  of  hydrocyanic  acid  yields  iso 
cyanides,  while  the  potassium  and  other  salts  yield  cyanides  with 
the  halogen  derivatives  of  the  hydrocarbons,  leads  us  to  suspect 
that  in  silver  cyanide  the  metal  may  be  in  combination  with 
nitrogen  and  not  with  carbon.  There  are  other  facts  known 
which  indicate  a  tendency  on  the  part  of  silver  to  unite  with 
nitrogen  in  carbon  compounds.  It  would  lead  too  far  to  discuss 
this  subject  here. 

It  seems  possible  that  isomeric  salts  of  cyanogen  may  be  dis- 
covered corresponding  to  the  cyanides  of  the  radicals  and  to  the 
isocyanides.  There  is  no  fact  known  which  makes  the  exist 


90  DERIVATIVES    OF   METHANE   AND   ETHANE. 

ence  of  two  potassium  cyanides  and  two  silver  cyanides  seem 
improbable.  The  two  series  of  salts  would  be  derivatives 
of  hydroc}ranic  acid,  H  — C— N,  and  isohydrocyanic  acid, 
H-N-C. 

Experiment  30.  The  odor  of  the  isocyauides,  as  has  been  stated, 
is  extremely  disagreeable,  arid  in  concentrated  form  it  is  unbearable. 
A  vivid  impression  in  regard  to  this  property  may  be  produced  by  the 
following  experiment.  In  a  test-tube  bring  together  a  little  chloroform, 
aniline,  and  alcoholic  potash.  The  reaction  takes  place  at  once.  It  is 
better  to  perform  the  experiment  out-of-doors,  and  in  such  a  place  that 
the  tube  with  its  contents  can  be  thrown  away  without  molesting  any 
one.  The  aniline  used  is  a  substituted  ammonia  analogous  to  methyl- 
amine,  containing  the  radical  C6H5  in  place  of  methyl.  The  isocyanide 
formed  has  the  formula  C6H5.  NC. 

CYANATES  AND  ISOCYANATES. 

There  are  two  series  of  compounds  bearing  to  cyanic  acid 
much  the  same  relation  as  that  which  the  cyanides  and  isocyan- 
ides  bear  to  hydrocyanic  acid. 

In  the  cyanates,  which  are  made  by  passing  cyanogen  chloride 
into  tbe  alcohols  (CH3OH  +  CNC1  =  CH3OCN  +  HC1) ,  the  radi- 
cal is  believed  to  be  united  to  the  cyanogen  group  by  means  of 
oxygen,  as  represented  in  the  formula  CH3— O  — CN. 

In  the  isocyauates  (first  called  cyanates) ,  on  the  other  hand, 
the  radical  is  believed  to  be  united  to  the  cyanogen  by  means 
of  nitrogen,  as  represented  thus,  CH3— N— CO.  The  isocyan- 
ates  are  made  by  distilling  potassium  cyanate  with  the  potassium 
salt  of  methyl-  or  ethyl-sulphuric  acid.  They  may  be  made  also 
by  bringing  together  the  iodides  of  radicals,  as  iodo-methane 
and  silver  cyanate.  They  are  very  volatile  substances,  which 
have  penetrating  and  suffocating  odors. 

One  of  the  principal  reactions  of  the  cyanates  is  that  which 
they  undergo  with  caustic  alkalies,  hydrochloric  acid,  etc.  They 
yield  cyanic  acid,  and  a  compound  containing  the  radical  which 
they  contained. 


ISOSULPHOCYANATES.  91 

The  isoc3Tanates  readily  3'ield  substituted  ammonias,  just  as 
the  isocyanicles  do  :  — 

C2H5-N-CO  +  H20  =  C2H5.NH2  +  CO2; 
CH3  -N-CO  +  H2O  -  CH3.NH2   +  CO2. 

The  views  held  in  regard  to  the  structure  of  the  cyauates  and 
isocyanates  are  based  upon  these  reactions,  which,  as  will  be 
observed,  are  very  similar  to  those  more  fully  considered  in 
discussing  the  difference  between  the  cyanides  and  isocyanides. 

The  existence  of  two  cyanic  acids,  and  of  two  series  of  salts 
derived  from  them,  seems  probable. 

SULPHO-CYANATES. 

The  ethereal  salts  of  sulphocyanic  acid  are  easily  made  by 
distilling  potassium  sulphocyanate  and  the  potassium  salt  of 
methyl-  or  ethyl-sulphuric  acid  :  — 

°^3>S04  +  KSCN  =  CH3SCN  +  K2SO4. 
K 

The  ethyl  compound,  which  is  very  similar  to  the  methyl  com- 
pound, is  a  liquid  boiling  at  146°. 

When  boiled  with  nitric  acid,  it  is  oxidized  to  ethyl-sulphonic 
acid.  Now,  it  has  been  shown  above  (see  p.  77) ,  that  in  ethyl- 
sulphonic  acid  the  ethyl  in  all  probability  is  in  combination  with 
the  sulphur.  It  hence  follows  that,  in  the  sulphocyanates 
obtained  from  potassium  sulphocyanate,  the  radical  is  also 
in  combination  with  sulphur,  as  indicated  in  the  formula, 
C2H5  — S  — CN.  This  view  is  supported  by  the  fact  that  ethyl 
sulpho-cyanate  readily  yields  ethyl  sulphide  as  a  product  of 
decomposition. 

ISO-SULPHO-CYANATES    OR   MuSTARD-OlLS. 

A  number  of  compounds  are  known  isomeric  with  the  sulpho- 
cyanates. The  best-known  member  of  the  class  is  ordinary 
bustard-oil.  Hence  they  have  been  called  mustard-oils,  and 


92  DERIVATIVES   OF   METHANE   AND   ETHANE. 

they  are  known  most  frequent!}'  by  this  name.  The  mustard- 
oils  are  made  by  means  of  a  series  of  somewhat  complicated 
reactions,  which  it  is  rather  difficult  to  interpret  without  a  com- 
parison with  some  similar  reactions  which  take  place  between 
simpler  substances. 

When  diy  ammonia  and  dry  carbon  dioxide  act  upon  each 
other,  so-called  anhydrous  ammonium  carbonate  is  formed.    This 

is  really  the  ammonium  salt  of  carbamic  acid,  CO  <  OH2.  Its 
formation  is  represented  thus  :  — 


Now,  remembering  that  carbon  bisulphide  is  similar  to  carbon 
dioxide,  and  that  ethyl-amine  is  similar  to  ammonia,  we  can 
readily  understand  the  reaction  which  takes  place  when  these 
two  substances  are  brought  together  :  — 


The  product  formed  is  the  ethyl-ammonium  salt  of  the  acid 

TO-TT/^t    'tT 

CS  <         2    °,  which  may  be  called  ethyl-sulpho-carbamic  acid. 

bH 

When  the  ethyl-ammonium  salt  is  treated  with  silver  nitrate,  the 


TT 

2   5 


corresponding  silver  salt,   cs<SAo.2   5»  ig  precipitated.     And 

finally,  when  this  salt  is  distilled,  it  breaks  up,  yielding  ethyl 
mustard-oil,  silver  sulphide,  and  hydrogen  sulphide  :  — 


5  =  2  SC-NC2H5  +  H2S  +  Ag2S. 

SAg 

Ethyl  mustard-oil  is  an  oily  liquid  which  does  not  mix  with 
water.  It  has  a  very  penetrating  odor,  and  acts  upon  the 
mucous  membranes  of  the  eyes  and  nose  in  the  same  way  as 
ordinary  oil  of  mustard.  The  properties  of  the  two  are  so  much 
alike  that  one  could  be  substituted  for  the  other. 


ISO-SULPHOCYANATES.  93 

Some  of  the  arguments  have  been  stated  which  lead  to  the 
view  that  in  the  sulpho-cyanates  the  radical  is  in  combination 
with  sulphur.  Having  once  accepted  this  view,  we  would 
naturally  suspect  that  in  the  mustard-oils  the  radical  is  in  com- 
bination with  nitrogen,  and  the  question  arises  whether  the 
reactions  of  these  bodies  are  of  such  a  character  as  to  justify 
this  suspicion?  They  certainly  are.  In  the  first  place,  when 
heated  with  water  or  with  hydrochloric  acid,  ethyl  mustard-oil  is 
decomposed,  yielding  ethyl-amine,  carbon  dioxide,  and  hydrogen 
sulphide  :  — 

SC-NC2H5  +  2  H2O  =  C2H5.NH2  +  H2S  +  CO2. 

And,  in  the  second  place,  nascent  hydrogen  converts  it  into 
ethyl-amine  and  formic  thioaldehyde  (i.e.,  formic  aldehyde  in 
which  the  oxygen  has  been  replaced  by  sulphur)  :  — 

SC-NC2H5  4-  4H  =  C2H5.NH2  +  H2CS. 

Thus,  as  will  be  seen,  the  tendency  of  the  sulpho-cyanates  is  to 
yield  sulphides  of  the  radicals  like  ethyl  sulphide,  (C2H5)2S  ; 
the  tendency  of  the  iso- sulpho-cyanates  is  to  yield  substituted 
ammonias,  like  ethyl-amine  NH2.C2H5.  These  facts  point  to 
the  relations  expressed  in  the  formulas,  R  —  S—  CN  for  the 
sulpho-cyanates,  and  R— N— CS  for  the  iso-sulpho-cyanates  or 
mustard-oils. 

In  reviewing  now  the  compounds  of  the  hydrocarbons  which 
are  related  to  cyanogen,  we  see  that  there  are  two  isomeric 
series  of  these,  the  names  and  general  formulas  of  which  are 
given  below :  — 

Cyanides,  R—C—N      .     .     .  Isocyanides  or  j  T?     ->r_n 

Carbamines,    j 

Cyanates,R— O  — CN    .     .     .   Isocyanates,  R— N— CO. 

Sulpho-cyanates,  R — S  —  CN   .  Iso-sulpho-cyan- 
ates or  Mus-  J-  R-N-CS. 
tard  oils, 


94  DERIVATIVES    OF   METHANE   AND    ETHANE. 

NOTE  FOR  STUDENT.  —  Study  these  compounds  until  the  exact  con- 
nection between  the  formulas  and  the  facts  above  stated  is  clearly 
seen. 

SUBSTITUTED  AMMONIAS. 

When  brom-ethane  or  any  similar  substitution-product  is 
treated  with  ammonia,  the  reactions  represented  by  the  follow- 
ing equations  take  place  step  by  step  :  — 

C2H5Br  +  NH3  =  NH2(C2H5).HBr ; 

C2H5Br  +  NH2(C2H5)  =  NH(C2H5)2.HBr ; 
C2H5Br  +  NH(C2H5)2  =  N(C2H5)3.HBr ; 

C2H5Br  +  N(C2H5)3     -  N(C2H5)4Br. 

The  first  three  products  are  salts  of  hydrobromic  acid,  and 
substances  which  in  all  their  properties  very  closely  resemble 
ammonia.  When  these  salts  are  distilled  with  potassium 
hydroxide  they  are  decomposed,  just  as  ammonium  bromide 
would  be.  Only  instead  of  getting  ammonia  and  potassium 
bromide,  we  get  the  compounds  ethyl-am  me,  NH2.C2H5,  di-etliyl- 
amine,  NH(C2H5)2,  and  tri-etliyl-amine,  N(C2H5)3.  These 
substances  may  be  regarded  as  derived  from  ammonia  by  the 
replacement  of  one,  two,  and  three  of  the  hydrogen  atoms 
respectively  by  ethyl.  The  last  product  of  the  series  of  reac- 
tions represented  above  may  be  regarded  as  ammonium  bromide, 
NH4Br,  in  which  all  four  hydrogen  atoms  are  replaced  by  ethyl 
groups. 

The  decomposition  by  potassium  hydroxide  of  the  first  two 
salts  is  represented  thus  :  — 

NH2(C2H5).HBr  +  KOH  =  NH2(C2H5)  +  KBr  +  H2O  ; 
NH(C2H5)2.HBr  +  KOH  =  NH(C2H5)2  +  KBr  +  H2O. 

Methyl-amine,  NH2.CH3.  —  This  compound  may  be  pre- 
pared by  treating  iodo-methane  with  ammonia  :  — 

CH3I  +  NH3  =  NH2CH3.HL 


DI-METHYL-AMLNE.  95 

It  was  first  made  by  treating  methyl  isocyanate,  CH3— N— CO, 
with  caustic  potash  :  — 

CH3-N-CO  +  H2O  =  NH2.CH3  -f  CO2. 

It  has  been  stated  that  it  is  formed  by  treating  hydrocyanic 
acid  with  nascent  hydrogen  :  — 

HCN  +  4H  =  NH2.CH3. 

It  occurs  in  nature  in  herring  brine,  and  is  one  of  the  products 
of  the  distillation  of  animal  matter  as  well  as  of  wood.  It  is 
now  prepared  on  the  large  scale  from  certain  waste  products 
obtained  in  the  refining  of  beet  sugar  (see  Tri-methyl-amine) . 

Methyl-amine  is  a  gas  which  is  easily  condensed  to  a  liquid. 
It  smells  like  ammonia.  It  is,  like  ammonia,  extremely  easily 
soluble  in  water,  1  volume  of  water  at  12.5°  taking  up  1150 
volumes  of  the  gas.  This  solution  acts  almost  exactly  like  a 
solution  of  ammonia  in  water.  It  is  strongly  alkaline.  It  pre- 
cipitates the  metallic  hydroxides,  but,  unlike  ammonia,  it  does 
not  redissolve  precipitated  hydroxides  of  nickel,  cobalt,  and 
cadmium  when  added  in  excess.  Like  ammonia,  it  dissolves 
aluminium  hydroxide. 

Methyl-amine  forms  salts  with  acids  in  the  same  way  that 
ammonia  does  ;  that  is,  by  direct  addition.  The  action  towards 
nitric  and  sulphuric  acids  takes  place  in  accordance  with  the 
following  equations  :  — 

NH2CH3  +  HN03  =  NH3CH3.N03; 
2  NH2CH3  +  H2S04  =  (NH3CH3)2SO4. 

These  salts  are  called  methyl-ammonium  nitrate  and  methyl- 
ammonium  sulphate  respectively. 

Di-methyl-amine,  NH(CH3)2.  —  This  is  formed  by  heating 
iodo-methane  with  alcoholic  ammonia  :  — 

2  CH3I  +  2  NH3  ==  NH(CH3)2.HI  +  NHJ. 


96  DERIVATIVES   OF   METHANE   AND  ETHANE. 

It  is  formed,  together  with  methyl-amine,  as  a  product  of  the 
distillation  of  wood. 

It  is  a  gas  which  condenses  to  a  liquid  at  +  8°-  Its  proper- 
ties are  much  like  those  of  methyl-amine. 

Tri-methyl-amine,  N(CH3)3.  — Tri-methyl-amine  is  formed 
as  one  of  the  products  of  the  treatment  of  iodo-methane  with 
ammonia.  It  occurs  widely  distributed  in  nature,  as  in  the 
blossoms  of  the  hawthorn,  the  wild  cherry,  and  the  pear.  It 
is  contained  in  herring  brine,  and  is  a  common  product  of  the 
decomposition  of  organic  substances  which  contain  nitrogen.  It 
is  now  obtained  in  large  quantities  from  the  so-called  ' '  vin- 
asses."  These  are  the  waste  liquids  obtained  in  the  refining  of 
beet  sugar.  When  the  "  vinasses"  are  evaporated  to-dryness, 
tri-methyl-amine  is  given  off  among  the  volatile  products.  It  is 
collected  as  the  hydrochloric  acid  salt,  N(CH3)3.HC1,  which, 
when  heated  to  260°,  yields  ammonia,  tri-methyl-amine,  and 
chlor-methane :  — 

3  N(CH3)3.HC1  =  2  N(CH3)3  +  NH3  +  3  CH3C1. 

The  chlor-methane  is  utilized  for  the  purpose  of  producing  low 
temperatures. 

Tri-methyl-amine  is  a  liquid  boiling  at  9°  to  10°.  It  has  a 
strong  ammoniacal  and  fishy  odor.  It  is  very  soluble  in  water 
and  alcohol,  and  is  a  strong  base.  It  is  used  in  the  prepara- 
tion of  potassium  carbonate,  by  the  Solvay  process.  In  making 
sodium  carbonate  from  the  chloride  by  this  method,  acid  ammo- 
nium carbonate  is  brought  together  with  the  chloride.  Thus 
mono-sodium  carbonate  is  precipitated,  and  ammonium  chloride 
is  left  in  solution.  But  mono-potassium  carbonate  and  ammo- 
nium chloride  are  about  equally  soluble,  so  that  potassium  car- 
bonate cannot  be  prepared  in  the  same  way.  On  the  other 
hand,  if  tri-methyl-amine  be  substituted  for  ammonia,  the  sepa- 
ration can  be  effected,  inasmuch  as  tri-methyl-ammonium  chlo- 
ride is  more  soluble  than  ammonium  chloride. 


TRI-METHYL-AMINE.  97 

NOTE  FOR  STUDENT.  —  Write  the  equations  representing  the  reac- 
tions involved  in  making  potassium  carbonate  from  potassium  chloride 
by  means  of  tri-methyl-amine. 

The  ethyl-amines  are  very  much  like  the  methyl  compounds, 
and  hence  need  not  be  specially  described. 

When  tri-ethyl-aniine  is  brought  together  with  iodo-ethane, 
the  two  unite,  forming  the  compound  tetra-ethyl-ammonium 
iodide,  N(C2H5)4I,  which  is  ammonium  iodide,  in  which  all  four 
hydrogen  atoms  have  been  replaced  by  ethyl  groups.  If  silver 
oxide  be  added  to  the  aqueous  solution  of  the  iodide,  silver 
iodide  is  precipitated,  and  by  evaporation  of  the  liquid  crystals 
of  tetra-ethyl-ammonium  hydroxide,  N(C2H5)4OH,  are  obtained. 
This  is  plainly  the  hypothetical  ammonium  hydroxide,  in  which 
the  four  ammonium  hydrogens  have  been  replaced  by  ethyl. 
Its  solution  acts  almost  like  caustic  potash.  It  is  very  caustic, 
attracts  carbon  dioxide  from  the  air,  saponifies  (see  p.  70) 
ethereal  salts,  and  gives  the  same  precipitates  as  caustic  potash. 
The  reactions  of  the  substituted  ammonias  above  described 
make  it  certain  that  these  bodies  are  very  closely  related  to 
ammonia.  The  methods  of  formation  also  point  clearly  to  the 
same  conclusion.  This  relation  is  best  expressed  by  the  form- 
ulas above  given. 

Another  method  for  the  formation  of  substituted  ammonias 
in  which  but  one  radical  is  present,  as  ethyl-amine,  NH2.C2H5, 
or  in  general  NH2 .  R,  consists  in  treating  with  nascent  hydro- 
gen compounds  known  as  nitro  compounds,  which  are  substitu- 
tion-products containing  the  group  (NO2)  in  the  place  of 
hydrogen.  Thus,  for  example,  when  nitro-methane,  CH3.NO2 
(which  see),  is  treated  with  hydrogen,  the  reaction  which  takes 
place  is  represented  thus :  — 

CH3.N02  +  6H  =  CH3.NH2  -f  2  H2O. 

In  connection  with  another  series,  it  will  be  shown  that  this 
reaction  is  a  most  important  one,  from  the  practical  as  well  as 
the  scientific  stand-point.  It  may  be  said  in  anticipation  that 


98  DERIVATIVES    OF   METHANE   AND    ETHANE. 

the  manufacture  of  aniline,  and  consequently  of  all  the  many 
valuable  dye-stuffs  related  to  aniline,  is  based  upon  this  reac- 
tion. 

Just  as  we  may  look  upon  methyl-amine  and  the  related  com- 
pounds, as  ammonia,  in  which  one  hydrogen  atom  is  replaced  by 
methyl,  so  also  we  may  regard  them,  and  with  equal  right,  as 
marsh  gas,  in  which  hydrogen  has  been  replaced  by  the  group  or 
residue  NH2.  Owing  to  the  frequency  of  the  occurrence  of  this 
group  in  carbon  compounds,  and  for  the  sake  of  simplifying  the 
nomenclature,  the  group  has  been  called  the  amide  or  amido 
group,  and  the  bodies  containing  it  amido -compounds.  Thus 
the  compounds  NH2 .  C2H5  may  be  called  either  etliyl-amine  or 
amido -ethane,  etc. 

Similarly,  those  bodies  which  contain  two  hydrocarbon  resi- 
dues, as  di-ethyl-amine,  NH(C2H5)2,  are  called  imido-compounds, 
and  the  group  NH  the  imide  or  imido  group.  Substituted 
ammonias  containing  one  hydrocarbon  residue  are  called  pri- 
mary ammonia  bases.  Those  containing  two  residues,  as  di- 
ethyl-amine,  NH(C2H5)2,  are  known  as  secondary  ammonia 
bases,  and  those  containing  three  residues,  as  tri-ethyl-amine, 
N(CH3)3,  are  called  tertiary  ammonia  bases. 

Among  the  most  important  of  the  reactions  of  amido-com- 
pounds  or  primary  bases  is  that  which  takes  place  when  they 
are  treated  with  nitrous  acid.  Take  ethyl-amine  as  an  illustra- 
tion. In  order  to  understand  what  takes  place  when  this 
compound  is  treated  with  nitrous  acid,  it  is  necessary  to  keep 
in  mind  the  fact  that  the  compound  itself  is  a  modified  ammo- 
nia, and  hence  we  may  expect  that  its  reactions  will  be  but 
modifications  of  those  which  take  place  with  ammonia.  Thus 
with  nitrous  acid  ammonia  unites  directly  to  form  ammonium 
nitrite  :  — 

NH3  -{-  HNO2  =  NH4.NO2. 

So  also  ethyl-amine  forms  ethyl-ammonium  nitrite  :  — 
NH2.C2H5  +  HNO2  =  NH3(C2H5).NO2. 


NITRO-COMPOUNDS.  99 

Now  we  know  that  ammonium  nitrite  breaks  up  readily  into 
free  nitrogen  and  water  :  — 

NH4.NO2  =  N2  +  H2O  +  H2O. 

So  also  ethyl-ammonium  nitrite  breaks  up  into  free  nitrogen, 
water,  and  alcohol :  — 

NH3(C2H5)NO2  =  N2  +  H2O  +  C2H5.OH. 

The  two  reactions  are  strictly  analogous.  As  in  the  second  case 
we  start  with  a  substituted  ammonia,  we  get  as  a  product  a 
substituted  water  or  alcohol. 

This  reaction  has  been  used  very  extensively  in  the  prepara- 
tion of  bodies  containing  hydroxyl.  For  ordinary  alcohol,  as 
is  clear,  it  is  not  a  convenient  method  of  preparation  ;  but  it 
will  be  shown  that  there  are  hydroxides  for  the  preparation  of 
which  it  is  by  far  the  most  convenient  method.  The  essential 
character  of  the  transformation  effected  by  it  will  be  best  under- 
stood by  comparing  the  formulas  of  the  amide  and  the  alcohol. 
We  have  ethyl-amine,  C2H5.NH2,  and  from  it  we  get  alcohol, 
C2H5.OH.  Thus  we  see  that  the  transformation  consists  in 
replacing  the  amido-group  by  hydrox}*!. 

HYDRAZINE  COMPOUNDS. 

Of  late  a  class  of  bodies  has  been  studied,  the  members  of 
which  bear  the  same  relation  to  the  hypothetical  body,  N.2H4 
(or  H2N  —  NIL) ,  that  the  substituted  ammonias  bear  to  ammo- 
nia. The  reactions  b}'  which  they  are  prepared  are  somewhat 
complicated,  and  they  do  not  play  an  important  part  in  the 
study  of  carbon  compounds.  A  mere  mention  of  their  exist- 
ence will  therefore  suffice  for  our  present  purpose. 

NlTRO-COMPOUNDS . 

Reference  has  already  been  made  to  a  class  of  bodies  con- 
taining the  group  NO2,  and  known  as  mtro-compounds.  They 
are  most  readily  made  by  treating  the  hydrocarbons  with  nitric 


100          DERIVATIVES   OF   METHANE   AND   ETHANE. 

acid.  This  method,  however,  is  not  applicable  to  the  hydro- 
carbons methane  and  ethane  and  their  homologues,  as  these  may 
be  treated  with  nitric  acid  without  undergoing  change.  The 
hydrocarbon  benzene,  C6H6,  is  acted  upon  very  easily  by  nitric- 
acid,  when  the  reaction  represented  by  the  following  equation 
takes  place  :  — 

C6H6  -f-  HO.NO2  =  C6H5.NO2  +  H2O. 

The  action  is  like  that  which  takes  place  between  sulphuric 
acid  and  benzene,  which  gives  the  sulphonic  acid  C6H5.SO2OH 

C1  TT 

or    6   5>SO2.     (Seep.  76.)     In  each  case  a  hydroxyl  of  the 

acid  is  replaced  by  the  simple  residue  of  the  hydrocarbon.  The 
product  in  the  case  of  the  bibasic  acid,  sulphuric  acid,  is  itself 
still  acid,  while  the  product  in  the  case  of  the  monobasic  nitric 
acid,  is  not  an  acid. 

The  nitro-derivatives  of  methane  have  been  made  by  a  reac- 
tion which  we  would  expect  to  yield  ethereal  salts  of  nitrous 
acid ;  namely,  by  treating  iodo-methane  or  ethane  with  silver 
nitrite :  — 

CH3I  +  AgNO2  =  CH3NO2  +  Agl. 

The  compound  CH3.NO2,  which  is  known  as  nitro-metliane, 
does  not  conduct  itself  like  the  ethereal  salts  of  nitrous  acid. 
The  latter  are  unstable  bodies,  while  the  former  is  stable. 

NOTE  FOR  STUDENT.  —  Compare  the  reaction  just  referred  to  with 
that  which  takes  place  between  silver  cyanide  and  iodo-methane ;  and 
that  which  takes  place  between  iodo-ethane  and  potassium  sulphite. 
What  analogy  is  there  to  the  former  and  to  the  latter? 

It  has  already  been  stated  that  the  nitro-derivatives  are  con- 
verted by  nascent  hydrogen  into  the  corresponding  amido- 
derivatives  (see  p.  97). 

NOTE  FOR  STUDENT.  —  Write  the  equations  representing  the  reac- 
tions necessary  to  convert  methyl  alcohol  into  methyl-amine  by  means 
of  the  nitro-compound. 


NITliOSO  AND   ISOiTl^OSO-OOMPOTJKDS.  101 


Nitroform,  CH(NO2)3,  a#  the  foiraula-'  iiiSieates/is  the  tri- 
nitro-derivative  of  methane,  or  tri-nitro-methane.  It  is  con- 
verted into  tetra-nitro-methane,  C(NO2)4,  when  treated  with  a 
mixture  of  concentrated  sulphuric  and  fuming  nitric  acids. 

Nitro-chloroform,  C(NO2)C13,  called  also  chlorpicrin  and 
nitro-trichlormethane,  is  formed  by  distilling  methyl  or  ethyl 
alcohol  with  common  salt,  saltpetre,  and  sulphuric  acid.  It  is 
formed  from  a  number  of  more  complicated  nitro-compounds, 
by  distilling  them  with  bleaching  lime  or  hydrochloric  acid  and 
potassium  chlorate. 

NITROSO-  AND  ISONITROSO- COMPOUNDS. 

When  a  compound  containing  the  group  CH  is  treated  with 
nitrous  acid,  a  reaction  takes  place,  which  is  represented  thus  :  — 

R.CH  +  HO. NO  =  R.C.NO  +  H2O. 

The  product  R.C.NO,  which  is  derived  from  the  original  sub- 
stance by  the  substitution  of  the  group  NO  for  a  hydrogen 
atom,  is  called  a  nitroso-compound.  By  oxidation  the  nitroso- 
compounds  are  converted  into  nitro-compounds,  and  by  reduc- 
tion they  yield  the  same  products  as  the  corresponding  nitro- 
compounds. 

The  isonitroso-compounds  are  isomeric  with  the  nitroso-com- 
pounds.  They  are  formed  whenever  acetones  or  aldehydes  are 
treated  with  hydroxylamine,  NH2,OH.  Assuming  that  the 
latter  substance  is  really  a  hydroxyl  derivative  of  ammonia,  the 
reaction  may  be  represented  thus  :  — 

CH3  CH3 

I  I 

CO  +  H,N.OH  =  C-N-OH  +  HX>. 

I  I 

CH3  CH3 

The  hydrogen  of  the  hydroxyl  has  acid  properties.  The  iso- 
nitroso-compounds are  readily  broken  up,  yielding,  as  one  of 
the  products,  hydroxylamine. 


102  DERIVATIVES    GF   METHANE   AND   ETHANE. 

Fulmitdc'  aoi'd,  C2N2O^Il2,  according  to  recent  investiga- 
tions, appears  to  be  an  isonitroso-compound,  and  for  that 
reason  finds  appropriate  mention  in  this  place.  The  principal 
compound  of  fulminic  acid,  is  the  mercury  salt,  C2N2O2Hg, 
commonly  known  as  fulminating  mercury.  It  is  prepared  by 
dissolving  mercury  in  strong  nitric  acid,  and  adding  alcohol  to 
the  solution.  It  is  extremely  explosive.  Mixed  with  potassium 
nitrate  it  is  used  for  filling  percussion-caps. 

When  fulminating  mercury  is  treated  with  concentrated  hydro- 
chloric acid,  it  yields  hydroxylamine  as  one  of  the  products  of 
decomposition.  This  is  regarded  as  evidence  that  fulminic  acid 
is  an  isonitroso-compound.  As  will  be  seen,  fulminic  acid  is 
isomeric  with  cyanic  and  cyanuric  acids  (see- pp.  83  and  84). 


CHAPTER   VII. 

DERIVATIVES  OF  METHANE  AND  ETHANE  CON- 
TAINING PHOSPHORUS,  ARSENIC,  ETC. 

Phosphorus  compounds. — Corresponding  to  the  amines  or 
substituted  ammonias  are  the  phosphines,  which,  as  the  name 
implies,  are  related  to  phosphine,  PH3.  Metlryl-phosphine, 
PH2.CH3,  di-methyl-phosphine,  PH(CH3)2,  and  tri-methyl- 
phosphine,  P(CH3)3,  may  be  taken  as  examples. 

These  substances,  like  the  corresponding  amines,  form  salts 
with  acids,  though  not  as  readily.  The  hydroxide,  tetra-ethyl- 
phospJionium  hydroxide,  P(C2H5)4.OH,  is  a  very  strong  base, 
though  not  as  strong  as  the  corresponding  nitrogen  derivative. 

The  "phosphines  have  one  marked  property  which  distin- 
guishes them  from  the  amines,  and  that  is  their  power  to  take 
up  oxygen  and  form  acids.  Thus,  ethyl-phosphine,  PH2.C2H5, 
when  treated  with  nitric  acid,  is  converted  into  ethyl-plios- 
pliinic  add,  PO(C2H5)  (OH)2,  a  bibasic  acid,  bearing  to  phos- 
phoric-acid the  same  relation  that  the  sulplionic  acids  bear  to 
sulphuric  acid. 

NOTE  FOR  STUDENT. — What  is  the  relation?  What  other  class  of 
acids  bears  the  same  relation  to  carbonic  acid? 

Di-ethyl-phosphine,  PH(C2H,)2,  yields  di-ethyl-phosphinic  acid, 
PO(C2H5)2.OH,  when  oxidized. 

These  compounds  are  not  commonly  met  with,  and  do  not 
play  a  very  important  part  in  the  study  of  the  compounds  of 
carbon. 

Arsenic  compounds.  —  The  most  characteristic  carbon 
compound  containing  arsenic  is  that  which  is  known  as  cacodyl, 


104          DERIVATIVES  OF  METHANE  AND  ETHANE. 

a  name  given  to  it  on  account  of  its  extremely  disagreeable 
odor  (from  KOKW&/S,  stinking)  .  It  is  prepared  by  distilling  a  rnix- 

ture  of  potassium  aeetate  :uul  arsenie  trioxide.  The  reactions 
which  take  place  are  very  complicated,  and  many  products  are 
formed.  chief  amon^  the  products  is  cacodyl  oxide:  — 


+  AsA  «  [(OH.)  .As]/)  +  2  K,COS  +  2  COt. 

NY  hen  treated  with  hydroehlorie  aeid.  tho  oxido  is  converted 
into  the  chtorhk  (01^)^801  ;  and,  when  the  chloride  is  treated 
with  zinc,  cacodyl  itself  is  produced.  Its  analysis  and  the 
determination  of  its  molecular  weight  lead  to  the  formula 

As_(\ll:,.  uhu'h  in  all  probability   should  be  represented    thus: 


5\  A    1  •     Cacodyl  appears  thus  as  a  compound  analogous 

L<.  H  ;  V.  As 

to  the  hydrazines  referred  to  above.     (See  p.  99.) 
NOTE  FOR  STUDENT.—  In  what  does  the  analogy  consist? 

Many  derivatives  of  cacodyl  have  been  made,  but  their  study 
would  hardly  be  profitable  to  the  beginner. 

By  treating  the  chlorides  of  silicon,  boron,  and  many  of  the 
metals  with  zinc  ethyl,  Zn(C2H5)2,  many  similar  ethyl  do  ma- 
tures have  been  made. 

Zino  ethyl  itself  is  made  by  treating  iodo-ethane  .  c  111. 
with  zinc  alone  or  with  zinc  sodium  :  — 

ZnNa,  +  2  CJ^I  =  Zn(Cya«)«  4-  2  Nal. 

It  is  a  liquid  boiling  at  118°.     It  takes  fire  in  the  air,  and  burns 
with  a  white  flame. 

Sodium-ethyl,  C^H&Na,  may  be  obtained  in  combination 
with  zinc  ethyl  by  treating  the  latter  with  sodium.  Both  these 
compounds  have  been  used  to  a  considerable  extent  in  the  syn- 
thesis of  carbon  compounds,  particularly  the  more  complex 
hydrocarbons,  and  they  will  be  frequently  referred  to  in  the 
following  pages. 


RETROSPECT,  10o 

NOTE  FOB  &TUDEXT. — What  i»  formed  when  sodium  methyl  and 
carbon  dioxide  are  allowed  to  act  upon  each  other? 

Many  of  the  derivative**,  like  the  above,  are  volatile  liquids. 
Such,  for  example,  are  mercury  ethyl,  Hg(CjH,)j,  aluminium 
ethyl,  A1(C2H,)«,  tin  tetretbyl,  Sn(C2H,)4,  and  silicon  tetrethyl, 
8i(CjH,)4.  The  study  of  these  compounds  has  been  of  assist- 
ance in  enabling  chemists  to  determine  the  atomic  weights  of 
some  of  the  elements  which  do  not  form  simple  volatile 
compounds. 

RETROSPECT. 

In  the  introductory  chapter  (p.  19)  these  words  were  used  in 
describing  the  plan  to  be  followed :  "  Of  the  first  series  of 
hydrocarbons  two  members  will  be  considered.  Then  the  de- 
rivatives of  these  two  will  be  taken  up.  These  derivatives  will 
serve  admirably  as  representatives  of  the  corresponding  deriva- 
tives of  other  hydrocarbons  of  the  same  series  and  of  other 
series.  Their  characteristics  and  their  relations  to  the  hydro- 
carbons will  be  dwelt  upon,  as  well  as  their  relations  to  each 
other.  Thus,  by  a  comparatively  close  study  of  two  hydro- 
carbons and  then*  derivatives,  we  may  acquire  a  knowledge  of 
the  principal  classes  of  the  compounds  of  carbon.  After  these 
typical  derivatives  have  been  considered,  the  entire  series  of 
hydrocarbons  win  be  taken  up  briefly,  only  such  facts  being 
dealt  with  at  all  fully  as  are  not  illustrated  by  the  first  two 
members." 

In  accordance  with  the  plan  thus  sketched  we  have  thus  far 
considered  the  principal  derivatives  of  the  two  hydrocarbons, 
methane  and  ethane,  so  far  as  these  derivatives  represent  dis- 
tinct classes  of  compounds.  These  derivatives  were  classified 
first  into  (1)  those  containing  halogens;  (2)  those  containing 
oxygen ;  (3)  those  containing  sulphur ;  and  (4)  those  contain- 
ing nitrogen.  On  examining  each  of  these  classes  more  closely, 
we  found  that  the  halogen  derivatives,  such  as  chlor-methane, 
brom-ethane,  etc.,  bear  very  simple  relations  to  each  other. 


104  DERIVATIVES    OF   METHANE   AND   ETHANE. 

a  name  given  to  it  on  account  of  its  extremely  disagreeable 
odor  (from  Ka/cwS^?,  stinking) .  It  is  prepared  by  distilling  a  mix- 
ture of  potassium  acetate  and  arsenic  trioxide.  The  reactions 
which  take  place  are  very  complicated,  and  many  products  are 
formed.  Chief  among  the  products  is  cacodyl  oxide :  — 

4CH3.CO2K  +  As2O3  =  [(CH3)2As]2O  +  2  K2CO3  +  2  CO2. 

When  treated  with  hydrochloric  acid,  the  oxide  is  converted 
into  the  chloride  (CH3)2AsCl;  and,  when  the  chloride  is  treated 
with  zinc,  cacodyl  itself  is  produced.  Its  analysis  and  the 
determination  of  its  molecular  weight  lead  to  the  formula 
As2C4H12,  which  in  all  probability  should  be  represented  thus : 

'    3  2   s  | .      Cacodyl  appears   thus  as  a  compound  analogous 

(  O  XAo  joxVS    ) 

to  the  hydrazines  referred  to  above.      (See  p.  99.) 
NOTE  FOR  STUDENT.  —  In  what  does  the  analogy  consist? 

Many  derivatives  of  cacodyl  have  been  made,  but  their  study 
would  hardly  be  profitable  to  the  beginner. 

By  treating  the  chlorides  of  silicon,  boron,  and  many  of  the 
metals  with  zinc  ethyl,  Zn(C2H5)2,  many  similar  ethyl  deriva- 
tives have  been  made. 

Zinc  ethyl  itself  is  made  by  treating  iodo-ethane,  C2H5I, 
with  zinc  alone  or  with  zinc  sodium :  — 

ZnNa2  +  2  C2H5I  =  Zn(C2H5)2  +  2  Nal. 

It  is  a  liquid  boiling  at  118°.  It  takes  fire  in  the  air,  and  burns 
with  a  white  flame. 

Sodium-ethyl,  CvH5Na,  may  be  obtained  in  combination 
with  zinc  ethyl  by  treating  the  latter  with  sodium.  Both  these 
compounds  have  been  used  to  a  considerable  extent  in  the  syn- 
thesis of  carbon  compounds,  particularly  the  more  complex 
hydrocarbons,  and  they  will  be  frequently  referred  to  in  the 
following  pages. 


RETROSPECT.  105 

NOTE  FOR  STUDENT.  —  What  is  formed  when  sodium  methyl  and 
carbon  dioxide  are  allowed  to  act  upon  each  other? 

Many  of  the  derivatives,  like  the  above,  are  volatile  liquids. 
Such,  for  example,  are  mercury  ethyl,  Hg(C2H5)2,  aluminium 
ethyl,  A1(C2H5)3,  tin  tetrethyl,  Sn(C2H5)4,  and  silicon  tetrethyl, 
Si(C2H5)4.  The  study  of  these  compounds  has  been  of  assist- 
ance in  enabling  chemists  to  determine  the  atomic  weights  of 
some  of  the  elements  which  do  not  form  simple  volatile 
compounds. 

RETROSPECT. 

In  the  introductory  chapter  (p.  19)  these  words  were  used  in 
describing  the  plan  to  be  followed :  "Of  the  first  series  of 
hydrocarbons  two  members  will  be  considered.  Then  the  de- 
rivatives of  these  two  will  be  taken  up.  These  derivatives  will 
serve  admirably  as  representatives  of  the  corresponding  deriva- 
tives of  other  hydrocarbons  of  the  same  series  and  of  other 
series.  Their  characteristics  and  their  relations  to  the  hydro- 
carbons will  be  dwelt  upon,  as  well  as  their  relations  to  each 
other.  Thus,  by  a  comparatively  close  study  of  two  hydro- 
carbons and  their  derivatives,  we  may  acquire  a  knowledge  of 
the  principal  classes  of  the  compounds  of  carbon.  After  these 
typical  derivatives  have  been  considered,  the  entire  series  of 
hydrocarbons  will  be  taken  up  briefly,  only  such  facts  being 
dealt  with  at  all  fully  as  are  not  illustrated  by  the  first  two 
members." 

In  accordance  with  the  plan  thus  sketched  we  have  thus  far 
considered  the  principal  derivatives  of  the  two  hydrocarbons, 
methane  and  ethane,  so  far  as  these  derivatives  represent  dis- 
tinct classes  of  compounds.  These  derivatives  were  classified 
first  into  (1)  those  containing  halogens;  (2)  those  containing 
ox}'gen ;  (3)  those  containing  sulphur ;  and  (4)  those  contain- 
ing nitrogen.  On  examining  each  of  these  classes  more  closely, 
we  found  that  the  halogen  derivatives,  such  as  chlor-methane, 
brom-ethane,  etc.,  bear  very  simple  relations  to  each  other. 


106          DERIVATIVES   OF   METHANE   AND   ETHANE. 

We  found  that  under  the  head  of  oxygen  derivatives,  the  most 
important  and  most  distinctly  characteristic  derivatives  of 
hydro-carbons  are  met  with ;  as,  the  alcohols,  ethers,  aldehydes, 
acids,  ethereal  salts,  and  ketones.  The  sulphur  derivatives, 
some  of  which  closely  resemble  the  oxygen  derivatives,  include 
the  sulphur  alcohols  or  mercaptans,  sulphur  ethers,  and  sulphonic 
acids. 

On  beginning  the  consideration  of  the  nitrogen  derivatives 
we  found  it  desirable  first  to  take  up  certain  derivatives  con- 
taining the  cyanogen  group,  among  which  are  cyanogen,  hydro- 
cj'anic  acid,  cyanic  acid,  and  sulphocyanic  acid.  Many  interest- 
ing carbon  compounds  are  closely  related  to  these  fundamental 
compounds.  Such,  for  example,  are  the  cyanides  and  carba- 
mines,  the  cyanates  and  isocyanates,  the  sulpho-cyanates  and 
iso-sulpho-cyanates  or  mustard-oils.  Following  the  compounds 
related  to  cyanogen,  we  took  up  the  interesting  compounds 
which  are  related  to  ammonia,  the  substituted  ammonias  or 
amines.  Then  came  the  nitro-derivatives ;  and,  finally,  the 
compounds  of  the  hydrocarbon  residues  or  radicals  with  metals. 

It  is  of  the  greatest  importance  that  the  student  should 
master  the  preceding  portion  of  this  book.  If  he  studies  care- 
fully the  reactions  which  have  been  considered,  and  which  are 
statements  in  chemical  language  which  tell  us  the  conduct  of 
the  various  classes  of  derivatives,  and  if  he  performs  the  ex- 
periments which  have  been  described,  he  will  have  a  fair  general 
knowledge  of  the  kinds  of  relations  which  are  met  with  in  con- 
nection with  the  compounds  of  carbon  through  the  whole  field. 
As  stated  in  the  Introduction  :  "  If  we  know  what  derivatives 
one  hydrocarbon  can  yield,  we  know  what  derivatives  we  may 
expect  to  find  in  the  case  of  every  other  hydrocarbon." 

The  more  the  student  practises  the  use  of  the  equations  thus 
far  given,  the  better  he  will  be  prepared  to  follow  the  remain- 
ing portions  of  the  book.  Indeed,  it  may  be  said  that,  if  he 
thoroughly  understands  what  has  gone  before,  what  follows  will 
appear  extremely  simple.  Whereas,  if  he  has  failed  at  any 


RETROSPECT.  107 

point  to  catch  the  exact  meaning,  if  he  has  failed  to  see  the 
connection,  he  had  better  go  back  and  faithfully  review,  or  he 
will  soon  find  his  mind  hopelessly  muddled,  and  relations  which 
are  as  clear  as  day  will  be  concealed  from  him. 

A  very  excellent  practice  is  to  trace  connections  between  the 
different  classes  of  compounds,  and  show  how  to  pass  from  one 
to  the  other.  Thus,  for  example,  (1)  show  by  what  reactions 
it  is  possible  to  pass  from  marsh  gas  to  acetic  acid.  (2)  How 
can  we  pass  from  ordinary  alcohol  to  ethylidene  chloride, 
CH3.CHC12?  (3)  What  reactions  would  enable  us  to  make 
methyl-amiue  from  its  elements?  (4)  How  may  acetone  be 
made  from  methyl-amine  ?  (5)  What  reactions  are  necessary  in 
order  to  make  ordinary  ether  from  ethyl-amine?  etc.,  etc.  It 
is  well  in  this  sort  of  practice  to  select  what  appear  to  be  the 
least  closely -related  compounds,  and  to  show  then  how  we  may 
pass  from  one  to  the  other.  Be  sure  to  select  representatives 
of  all  the  classes  hitherto  mentioned,  and  to  bring  in  all  the 
important  reactions. 


CHAPTER  VIII. 

THE    HYDROCARBONS    OF    THE    MARSH-GAS 
SERIES,    OR   PARAFFINS. 

THE  existence  of  the  homologous  series  of  Irydrocarbons  be- 
ginning with  methane  and  ethane  was  spoken  of  before  its  first 
two  members  were  considered.  A  general  idea  of  the  extent 
of  the  series,  and  of  the  names  used  to  designate  the  members, 
may  be  gained  from  the  following  table  :  — 

MARSH-GAS    HYDROCARBONS. 
PARAFFINS.  —  HYDROCARBONS,  CnH2n  +  2. 

Boiling-Point. 

Methane      ....  CH4  .  .  .  gas. 

Ethane  .     .     .     .     .  C2H6  .  .  .  gas. 

Propane      ....  C3H8  .  .  .  gas. 

Butane C4H10  ...  1°. 

Pentane      ....  C5H12  .  .  .  38°. 

Hexane       ....  C6H14  .  .  .  70°. 

Heptane     ....  C7H16  .  .  .  98.4°. 

Octane C8H18  .  .  .  125°. 

Nonane       ....  0^  .  .  .  148°. 

Dodecane  ....  C^H^  .  .  .  202°. 

Hecdecane       .     .     .  C]6H34  .  .  .  278°. 

The  explanation  of  the  remarkable  relation  in  composition 
existing  between  these  members,  a  relation  to  which  the  name 
homology  is  given,  has  already  been  referred  to  (p.  22).  The 
number  of  hydrogen  atoms  contained  in  a  member  of  this  series 


PETROLEUM.  109 

bears  a  constant  relation  to  the  number  of  carbon  atoms,  as 
expressed  in  the  general  formula  CnH2n  +  2.  On  examining  the 
column  headed  "  Boiling-Point "  it  will  be  seen  that,  as  we  pass 
upward  in  the  series,  the  boiling-point  becomes  higher  and  higher. 
The  first  three  members  are  gases  at  ordinary  temperatures,  while 
the  last  boils  at  278°.  The  elevation  in  the  boiling-point  is 
to  some  extent  regular,  as  will  be  observed.  The  difference 
between  butane,  C4H10,  and  pentane,  C5H12,  is  38  —  1  =  37°  ; 
that  between  pentane  and  the  next  member  is  70  —  38  =  32°  ; 
between  hexane  and  heptane  it  is  98.4  —  70  =  28.4°  ;  between 
heptane  and  octane,  125  —  98.4  =  26.6°  ;  and,  finally,  between 
octane  and  nonane  the  difference  is  148—  125  =  23°.  Thus  it 
will  be  seen  that  the  elevation  in  boiling-point  caused  by  the 
addition  of  CH2  decreases  as  we  pass  upward  in  the  series. 
Other  relations  have  been  pointed  out,  but  it  would  be  prema- 
ture to  discuss  them  here. 

The  chief  natural  source  of  the  paraffins  is  petroleum ;  but 
although  this  substance,  which  occurs  in  such  enormous  quanti- 
ties in  nature,  undoubtedly  contains  a  number  of  the  members 
of  the  paraffin  series,  it  is  an  extremely  difficult  matter  to 
isolate  them  from  the  mixture.  Prolonged  fractional  distilla- 
tion is  not  sufficient  for  the  purpose.  If,  however,  some  of  the 
purest  products  which  can  thus  be  obtained  be  treated  with 
concentrated  sulphuric  acid,  and  afterwards  with  concentrated 
nitric  acid,  and  then  washed  and  redistilled,  they  may  be 
obtained  in  pure  condition. 

Petroleum.  —  Petroleum  occurs  in  enormous  quantities  in 
several  places.  Among  the  most  important  localities  are 
Pennsylvania,  the  Crimea,  the  Caucasus,  Persia,  Burmah, 
China,  etc.  In  some  places  it  issues  constantly  from  the  earth. 
Usually  it  is  necessary  to  bore  for  it.  When  one  of  the  cavi- 
ties in  which  it  is  contained  is  punctured,  the  oil  is  forced  out 
of  a  pipe  inserted  into  the  opening  in  a  jet,  in  consequence  of 
the  pressure  exerted  upon  it  by  the  gaseous  constituents.  As 


110        HYDROCARBONS   OF   THE   MARSH-GAS    SERIES. 

first  obtained,  it  is  usually  a  dark,  3Tellowish-green  liquid,  with 
an  unpleasant  odor.  It  varies  in  appearance  according  to  the 
place  in  which  it  is  found.  American  petroleum  contains  the 
lowest  members  of  the  paraffin  series  ;  and  when  the  oil  is 
exposed  to  the  air  the  gases  are  given  off. 

Refining  of  petroleum.  To  render  petroleum  fit  for  use  in 
lamps,  it  is  necessary  that  the  volatile  portions  should  be 
removed,  as  they  form  explosive  mixtures  with  air,  just  as 
marsh  gas  does.  It  is  also  necessary  to  remove  the  higher 
boiling  portions,  because  they  are  semi-solid,  and  would  clog 
the  wicks  of  the  lamps.  The  crude  oil  is  therefore  subjected  to 
distillation,  and  only  those  parts  which  have  a  certain  specific 
gravity  or  boil  between  certain  points  are  used  for  illuminating 
purposes,  under  the  name  of  kerosene.  Besides  being  distilled, 
the  oil  must  further  be  treated  with  concentrated  sulphuric 
acid,  which  removes  a  number  of  undesirable  substances,  and 
afterwards  with  an  alkali,  and  then  with  water.  All  these 
processes  taken  together  constitute  what  is  called  the  refining 
of  petroleum.  In  the  distillation,  the  lighter  products  are 
usually  divided  into  several  parts,  according  to  the  specific 
gravity  or  boiling-point.  Thus  we  have  the  products  cymogene, 
rhigolene,  gasoline,  naphtha,  and  benzine,  all  of  which  are 
lighter  than  kerosene.  It  must  be  distinctly  understood  that 
none  of  the  substances  here  mentioned  are  pure  chemical  sub- 
stances. The  names  are  commercial  names,  each  of  which 
applies  to  a  complex  mixture  of  hydrocarbons.  From  the 
heavier  products,  that  is,  those  that  boil  at  higher  tempera- 
tures than  the  highest  limit  for  kerosene,  paraffin,  which  is  a 
mixture  of  the  highest  members  of  this  series,  is  made. 

Owing  to  the  danger  attendant  upon  the  use  of  improperly 
refined  petroleum,  laws  have  been  enacted  relating  to  the 
properties  which  the  kerosene  exposed  for  sale  must  have. 
These  laws,  which  differ  somewhat  in  different  countries  and 
different  parts  of  the  same  country,  relate  mostly  to  what  is 
called  the  Jlashing -point.  This  is  the  temperature  to  which  the 


SYNTHESIS    OF   THE   PARAFFINS. 


Ill 


oil  must  be  heated  before  it  takes  fire  when  a  flame  is  applied 
to  it.  The  legal  flashing-point  in  many  parts  of  the  United 
States  is  44°.  Various  forms  of  apparatus  have  been  de- 
vised for  the  purpose  of  making  the  determination  of  the 
flashing-point  as  accurately  as  possible.  Among  them  the  fol- 
lowing commends  itself  by  its  simplicity  : 
The  cylinder  A  is  2  to  3cm  in  diameter  and 
10  to  12cm  long.  Just  within  the  wooden 
cork  the  bent  tube  contracts  to  a  small 
orifice.  At  d  it  is  connected  by  rubber- 
tubing  with  a  source  of  compressed  air 
(hand-bellows  or  gas  holder) ,  the  flow  of 
which  can  be  controlled  by  the  pinch-cock. 
A  is  about  one-third  filled  with  kerosene, 
and  secured  in  a  clamp,  so  that  it  plunges  in 
a  water-bath  to  the  level  of  the  oil.  Air  is 
now  passed  through  deb,  and  e  so  adjusted  that  about  0.5cm 
foam  is  kept  on  the  surface  of  the  oil.  From  degree  to  degree 
the  test  is  made  by  bringing  a  small  flame  for  an  instant  to  the 
mouth  of  A.  At  the  flashing-point  the  vapor  ignites,  and  the 
bluish  flame  runs  down  to  the  surface  of  the  oil. 


Fig. 


Experiment  31.  Make  an  apparatus  like  the  above,  and  determine 
the  flashing-points  of  two  or  three  specimens  of  kerosene  which  may 
be  available. 

Synthesis  of  the  paraffins.  —  Although  the  paraffins  do 
occur  in  nature,  and  some  of  them  may  be  obtained  in  pure  con- 
dition from  natural  sources,  we  are  dependent  upon  synthetical 
operations  performed  in  the  laboratory  for  our  knowledge  of 
the  series  and  the  relations  existing  between  them. 

We  have  already  seen  how  ethane  may  be  prepared  from 
methane  b}^  treating  methyl  iodide  with  zinc  or  sodium,  as  repre- 
sented in  this  equation  :  — 


CH3I  +  CH3I  +  2  Na  =  C2H6  +  2  Nal. 


112         HYDROCARBONS    OF    THE    MARSH-GAS    SERIES. 

This  method  has  been  extensively  used  in  the  building  up  of 
higher  members  of  the  series.  Thus  from  ethane  we  may  make 
ethyl  iodide,  and  by  treating  this  with  sodium  get  butane 
C4H]o :  — 

C2H5I  +  C2H5I  +  2  Na  =  C4H10  +  2  Nal. 

But  we  may  get  the  intermediate  member,  propane,  C3H8,  by 
mixing  methyl  iodide  and  ethyl  iodide  and  treating  the  mixture 
with  sodium :  — 

CH3I  +  C2H5I  +  2  Na  =  CH3.C2H5  +  2  NaL 

By  applying  this  method,  it  is  plain  that  a  large  number  of  the 
members  of  the  paraffin  series  might  be  made. 

Another  method  consists  in  treating  the  zinc  compounds  of 
the  radicals,  like  zinc  etlryl,  Zn(C2H5).2,  with  the  iodides  of  rad- 
icals. Thus  zinc  methyl  and  methyl  iodide  give  ethane  ;  zinc 
ethyl  and  ethyl  iodide  give  butane ;  zinc  ethyl  and  methyl 
iodide  give  propane,  etc.  :  — 

Zn(CH3)2  +  2CH3I  =  2  C2H6  +  ZnI2 ; 
Zn(C2H5)2  +  2  C2H5I  =  2  C4H10  +  ZnI2 ; 
Zn(QH5)2  +  2  CH3I  =  2  C3H8  +  ZnI2. 

Paraffins  may  be  made  by  replacing  the  halogen  in  a  substitu- 
tion-product by  hydrogen.  This  may  be  effected  by  nascent 
hydrogen  or  by  hydriodic  acid  :  — 

C4H9I  +  2  H  =  C4H10  +  HI. 

Finally,  the  paraffins  may  be  made  by  heating  the  acids  of  the 
formic  acid  series  with  an  alkali.  This  has  been  illustrated  by 
the  preparation  of  marsh  gas  from  acetic  acid  by  heating  with 
lime  and  caustic  potash.  The  reaction  may  be  written  thus  :  — 

CH3.CO2K  +  KOH  =  CH4  +  CO3K2. 
The  products  are  a  hydrocarbon  and  a  carbonate. 


ISOMERISM   AMONG   THE   PARAFFINS.  113 

Isomerism  among-  the  paraffins.  —  It  has  already  been 
stated  that  the  evidence  is  almost  conclusive  that  each  of  the 
four  hydrogen  atoms  of  marsh  gas  bears  the  same  relation  to  the 
carbon,  and  hence  we  believe  that,  as  regards  the  nature  of  the 
product,  it  makes  no  difference  which  hydrogen  atom  is  replaced 
by  a  given  atom  or  radical.  According  to  this,  as  ethane  is  the 
methyl  derivative  of  marsh  gas,  it  makes  no  difference  which  of 
the  Irydrogen  atoms  of  marsh  gas  is  replaced  by  the  methyl,  the 
product  must  always  be  the  same,  or  there  is  but  one  ethane 

possible   according  to  the  theory.     This  is   represented   by  the 

H     H 

I        I 
formula,  H  —  C  —  C  —  H,  or  H3C  —  CH3.     In  ethane,  as  well  as  in 

H     H 

methane,  all   the  hydrogen  atoms  bear  the   same  relation   to 
the  molecule,  and  it  should  make  no  difference  which  one  is 
replaced  by  methyl.     But  propane  is  regarded  as  derived  from 
ethane  by  the  substitution  of  methyl  for  hydrogen;  .and,  as  it 
makes    no  difference  which  hydrogen  is  replaced,  there  is  but 
one  propane  possible.     Only  one  has  ever  been  discovered,  and 
this  must  be  represented  thus  :  — 
H      H      H 
I        I        I 
H  -  C  -  C  -  C  -  H,  or   CH3.CH2.CH3. 

I      I      i 

H      II      II 

Now,  continuing  the  process  of  substitution  of  methyl  for  hydro- 
gen, it  appears  that  the  theory  indicates  the  possibilit}'  of  the 
existence  of  two  compounds  of  the  formula  C4H10.  One  of 
these  should  be  obtained  by  replacing  by  methyl  one  of  the  three 
hydrogens  of  either  methyl  group  of  propane.  It  is  represented 
by  the  formula  :  — 

H      H     H     H 

I  I  I  I 
H  -  C  -  C  -  C  -  C  -  H,  or  H3C.CH2.CH2.CH3. 

I  I  I  I 
H  H  H  H 


114        HYDROCARBONS    OF   THE   MARSH-GAS    SERIES. 

The  other  should  be  obtained  by  replacing  by  methyl  one  of  the 
two  hydrogens  of  the  group  CH2  contained  in  propane.  This 
would  give  a  hydrocarbon  of  the  formula  :  — 

H      H      II  CH3 

III  I 

H-C-C-C-H,  or  CH3  -  CH  -  CH3. 

I        I        I 
H      C     H 


H    H    II 

The  theory  then  indicates  the  existence  of  two  butanes.  How 
about  the  facts?  Two,  and  only  two  butanes  have  been  discov- 
ered. The  first,  which  occurs  in  American  petroleum,  has  been 
made  synthetically  by  treating  ethyl  iodide  with  zinc  :  — 

2CH3.CHJ  +  Zn  =  CH3.CH2.CH2.CH3  +  ZnI2. 

The  method  of  synthesis  clearly  shows  which  of  the  two  possi- 
ble isomerides  the  product  is.  It  is  known  as  normal  butane. 
It  is  a  gas  which  can  be  condensed  to  a  liquid  at  +1°. 

The  second,  or  isobutane,  is  made  from  an  alcohol  which 
will  be  shown  to  have  the  structure  represented  by  the  formula 
CH3 
I 
CH3  —  C  —  OH  (see  Tertiary  Butyl  Alcohol,  p.  124) ,  by  replacing 

CH3 

the  hydroxyl  by  hydrogen.  It  is  a  gas  which  becomes  liquid 
at  -17°. 

The  differences  between  the  two  butanes  are  observed  princi- 
pally in  their  derivatives. 

Applying  the  same  method  of  consideration  to  the  next 
member  of  the  series,  how  many  isomeric  varieties  of  pentane, 
CH12,  may  we  expect  to  find  ?  The  question  resolves  itself  into 
a  determination  of  the  number  of  kinds  of  hydrogen  atoms  con- 
tained in  the  two  butanes,  or  the  number  of  relations  to  the 
molecule  represented  among  the  hydrogen  atoms  of  the  butanes. 


PENTANES.  115 

We  can  make  this  determination  best  by  examining  the  struc- 
tural formulas.  Take  first  normal  butane  :  — 

H      H      H      H 

I        I        I        I 

H-C-C-C-C-H. 

I        I        I        I 
H     H     H     H 

In  this  there  are  plain!}'  two  different  relations  represented ; 
viz.,  that  of  each  of  the  six  hydrogens  in  the  two  methyl  groups, 
and  that  of  each  of  the  four  hydrogens  of  the  two  CH2  groups. 
The  two  possible  methyl  derivatives  of  a  hydrocarbon  of  this 
formula  are  therefore  to  be  represented  thus  :  — 

H3C.CH2.CH2.CH2.CH3,  (1) 

PTT 

and  H3C.CH2.CH<^3.  (2) 

CH3 

CH3 

Now,  taking  isobutane,  HC  —  CH3,  we  see  that  it  consists  of 

I 

CH3 

three  methyl  groups,  giving  nine  hydrogen  atoms  of  the  same 
kind,  and  one  CH  group,  the  hydrogen  of  which  bears  a  dif- 
ferent relation  to  the  molecule  from  that  which  the  other  nine 
do.  There  are  therefore  two  possible  methyl  derivatives  of 
isobutane  which  must  be  represented  thus  :  — 

CH3  CH3 

I  I 

HC  -  CH2.CH3  (3),  and  H3C  -  C  -  CH3.  (4) 

I  I 

CH3  CH3 

We  have,  therefore,  apparently  four  pentanes.  But  on  compar- 
ing formulas  (2)  and  (3),  it  will  be  seen  that,  though  written  a 
little  differently,  they  really  represent  one  and  the  same  com- 
pound. Thus  the  number  of  pentanes,  the  existence  of  which 
is  indicated  by  the  theory,  is  three,  and  these  are  represented 


116        HYDROCARBONS    OF   THE   MARSH-GAS    SERIES. 

by  formulas  (1),  (2),  and  (4).  They  are  all  "known.  The 
first  is  called  normal  pentane,  the  second  iso-pentane  or 
di-methyl-ethyl-methane,  and  the  third  tetra-methyl-me- 
thane. 

It  would  lead  too  far  to  discuss  all  the  methods  of  prepara- 
tion and  the  properties  of  these  hydrocarbons.  It  will  be  seen 
that  the  methods  of  preparation  show  what  the  structure  of  a 
hydrocarbon  is.  Di-metlryl-ethyl-methane  is  made  from  an 
alcohol  which  can  be  shown  to  have  the  formula 

^H3>CH.CH2.CH2OH, 
CH3 

by  replacing  the  hydroxyl  by  hydrogen.  Hence  its  structure  is 
that  represented  above  by  formulas  (2)  and  (3). 

Tetra-methyl-methane  is  made  by  starting  with  acetone. 
Acetone  has  been  shown  to  consist  of  carbonyl  in  combina- 
tion with  two  methyl  groups,  as  represented  in  the  formula 
CH3— CO— CH3.  It  has  also  been  shown  that,  by  treating 
acetone  with  phosphorus  pentachloride,  the  oxygen  is  replaced 
by  chlorine,  giving  a  compound  of  the  formula  CH3—  CC12— CH3. 
Now,  b}r  treating  this  chloride  with  zinc-methyl,  the  chlorine  is 
replaced  by  methyl  thus  :  — 

CH3 
I 

CH3-CC12-CH3  -f  Zn(CH3),  =  CH3-C-CH3  +  ZnCl2. 

I 
CH3 

The  product  is  tetra-methyl-methane,  and  the  synthesis  thus 
effected  shows  at  once  what  the  structure  of  the  product  is. 

Hexanes.  —  The  student  will  now  be  prepared  to  apply  the 
theory  to  the  determination  of  the  number  of  hexanes  possible. 
He  will  find  that  there  are  five.  The  theory  is,  in  this  case  as  in 
the  preceding,  in  perfect  accordance  with  the  facts.  There  are 
five  and  only  five  hexanes  known.  Only  the  names  and  formu- 
las of  these  will  be  given  here  :  — 


HEXANES.  117 

1.  Normal  hexane,  CH3.CH2.CH2.CH2.CH2.CH3. 

2.  Iso-hexane,  CH3.CH2.CH2.CH  <  ^3. 

CH3 

3.  Methyl-di-ethyl-methane,  C 


CH2vCH3 

4.  Tetra-methyl-ethane,  ^>HC-CH<^3 

H3O  v^H3 

CH3 
I 

5.  Tri-methyl-ethyl-methane,  H3C-C-CH2.CH3. 

I 
CH3 

Passing  upward,  we  find  that  nine  heptanes  are  possible 
according  to  the  theory,  while  but  four  have  thus  far  been 
discovered  ;  and  that,  while  theory  indicates  the  possibility  of 
the  discovery  of  eighteen  hydrocarbons  of  the  formula  C8H18,  but 
three  are  known.  The  theoretical  number  of  isomeric  varieties 
of  the  highest  members  of  the  series  is  very  great,  but  our 
knowledge  in  regard  to  these  highest  members  is  very  limited. 
and  it  is  impossible  to  say  whether  the  theory  will  ever  be 
confirmed  by  facts.  It  may  be  that  there  is  some  law  limiting 
the  number  of  complicated  hydrocarbons.  It  is,  however,  idle 
to  speculate  upon  the  subject  at  present.  It  is  well  for  us  to 
keep  in  mind  that  a  thorough  knowledge  of  a  few  of  the  simplest 
members  of  the  series  is  all  that  is  necessary  for  the  present. 

On  examining  the  formulas  used  to  express  the  structure  of 
the  hydrocarbons,  we  find  that  they  may  be  divided  into  three 
classes  :  — 

(1)  Those  in  which  there  is  no  carbon  atom  in  combination 
with  more  than  two  others  ;  as,  — 

Propane  ....  CH3.CH2.CH3; 
Normal  butane  .     .  CH3.CH2.CH2.CH3  ; 
Normal  pentane     .  CH3.CH2.CH,  .CH2.CH3  ; 
and          Normal  hexane  .     .  CH3  .CH2  .CH2  .CH2  .CH2  .CH;;. 


118        HYDROCARBONS    OF   THE   MARSH-GAS    SERIES. 

(2)   Those  in  which  there   is  at  least  one    carbon   atom  in 
combination  with  three  others;    as,  — 

Isobutane  .     .     .     .  CH3  .CH  <  ^3  ; 

LH3 

Isopentane      ...  CH3.CH2.CH<^3; 

CH3 

Isohexane  .     .     .     .  CH3  .CH2  .CH2  .CH2  <  ^Hs  ; 

CH3 

and         Tetra-methyl-ethane,  H     >  CH  -  CH  <  ™3. 


(3)  Those  in  which  there  is  at   least  one  carbon  atom  in 
combination  with  four  others;    as,  — 


Tetra-methyl- 
methane 


CH3 

I 


}    •     ..CH3-C-CH3; 


I 
CH, 


CH3 

and        ^^-^.CA-i- 

methane  j 

CH3 


The  members  of  the  first  class  are  called  normal  paraffins; 
those  of  the  second  class,  iso-paraffins;  and  those  of  the  third 
class,  neo-paraffins. 

Only  the  members  of  the  same  class  are  strictly  comparable 
with  each  other.  Thus  it  has  been  found  that  the  boiling-points 
of  the  normal  hydrocarbons  bear  simple  relations  to  each  other, 
and  that  the  same  is  true  of  the  iso-paraffins  ;  but,  on  compar- 
ing the  boiling-points  and  other  physical  properties  of  normal 
paraffins  with  those  of  the  iso-  or  neo-paraffins,  no  such  simple 
relations  are  observed. 


NOMENCLATURE.  119 

Regarding  the  names  of  the  paraffins,  the  simplest  nomen- 
clature in  use  is  that  according  to  which  the  hydrocarbons  are 
all  regarded  as  derivatives  of  methane.  Thus  we  get  the 


name  ethyl-methane  for  propane,  C  -j  „      ;  tri-methyl-methane 
<  CH3  f  CH3 

CH  '  CH 

for  isobutane,  C  \       *  ;  tetra-methyl-  methane,  C  -j  ntT3,  etc. 
CH3  CH3 


H  CH3 


CHAPTER   IX. 

OXYGEN  DERIVATIVES    OP    THE   HIGHER  MEM- 
BERS OP  THE  PARAFFIN  SERIES. 

WE  are  now  to  take  up  the  derivatives  of  the  higher  mem- 
bers of  the  paraffin  series,  just  as  we  took  up  the  derivatives  of 
methane  and  ethane.  Not  much  need  be  said  in  regard  to  the 
halogen  derivatives.  A  few  of  them  will  be  mentioned  in  con- 
nection with  the  corresponding  alcohols.  The  chief  substances 
which  will  require  attention  are  the  alcohols  and  acids. 

1.  ALCOHOLS. 

Normal  propyl  alcohol,  C3HT.OH.  —  When  sugar  under- 
goes fermentation,  a  little  propyl  alcohol  is  always  formed,  and 
is  contained  in  the  "  fusel  oil."  From  this  it  may  be  separated 
by  treating  those  portions  which  boil  between  85°  and  110° 
with  phosphorus  and  bromine.  The  bromides  of  the  alcohols 
present  are  thus  formed  (what  is  the  reaction  ?) ,  and  these  are 
separated  by  fractional  distillation.  The  bromide  correspond- 
ing to  propyl  alcohol  is  then  converted  into  the  alcohol  (how 
may  this  be  doue?). 

It  is  a  colorless  liquid  with  a  pleasant  odor.  It  boils  at  97.4° 
(compare  with  the  boiling-points  of  methyl  and  ethyl  alcohol) . 
It  conducts  itself  almost  exactly  like  the  two  first  members  of 
the  series.  By  oxidation  it  is  converted  into  an  aldehyde, 
C3H6O,  and  an  acid,  C3H6O2,  which  bear  to  it  the  same  relations 
that  acetic  aldehyde  and  acetic  acid  bear  to  ethyl  alcohol. 

Secondary  propyl  or  isopropyl  alcohol,  C3H7.OH.  — 
The  reasons  for  regarding  the  alcohols  as  hydroxyl  derivatives 


SECONDARY   ALCOHOLS.  121 

of  the  hydrocarbons  have  been  given  pretty  fully.  As  the  six 
hydrogen  atoms  of  ethane  are  all  of  the  same  kind,  but  one 
ethyl  alcohol  appears  to  be  possible  and  only  one  is  known. 
But  just  as  there  are  two  butanes  or  methyl  derivatives  of  pro- 
pane, so  there  are  two  hydroxyl  derivatives  of  propane  ;  or,  in 
other  words,  two  propyl  alcohols.  The  first  is  the  one  obtained 
from  "  fusel  oil,"  the  other  is  the  one  called  secondary  propyl 
alcohol.  This  has  already  been  referred  to  under  the  head  of 
Acetone  (see  p.  72),  where  it  was  stated  that  acetone  is  con- 
verted into  secondary  propyl  alcohol  by  nascent  hydrogen. 
We  are,  in  fact,  dependent  upon  this  method  for  the  prepara- 
tion of  the  alcohol. 

It  is,  like  'ordinary  propyl  alcohol,  a  colorless  liquid.  It 
boils  at  85°.  While  all  its  reactions  show  that  it  is  a  hydroxide, 
under  the  influence  of  oxidizing  agents  it  conducts  itself  quite 
differently  from  the  alcohols  thus  far  considered.  It  is  con- 
verted first  into  acetone,  C3H6O,  which  is  isomeric  with  the 
aldeh}"de  obtained  from  ordinary  propyl  alcohol  ;  by  further 
oxidation,  it  however  does  not  yield  an  acid  of  the  formula 
C3H6O2,  as  we  would  expect  it  to,  but  breaks  down,  yielding 
two  simpler  acids;  viz.,  formic  acid,  CH2O2,  and  acetic  acid, 


Secondary  alcohols.  —  Secondary  propyl  alcohol  is  the 
simplest  representative  of  a  class  of  alcohols  which  are  known 
as  secondary  alcohols.  They  are  made  by  treating  the  ketones 
with  nascent  hydrogen,  and  are  easily  distinguished  from  other 
alcohols  by  their  conduct  towards  oxidizing  agents.  The}* 
yield  acetones  containing  the  same  number  of  carbon  atoms, 
and  then  break  down,  yielding  acids  containing  a  smaller  num- 
ber of  carbon  atoms. 

Is  there  anything  in  the  structure  of  these  secondary  alcohols 
to  suggest  an  explanation  of  their  conduct?  Secondary  pro- 
pyl alcohol  is  made  from  acetone  by  treating  with  nascent 
hj'drogen.  Acetone  contains  two  methyl  groups  and  carbonyl, 


122  DERIVATIVES   OF   THE  PARAFFINS. 

as  represented  by  the  formula  CH3— CO  — CH3.  The  sim- 
plest change  that  we  can  imagine  as  taking  place  in  this  com- 
pound under  the  influence  of  hydrogen  is  that  represented  in 
the  following  equation  :  — 

CH3-CO-CH3  +  H2  =  CH3-CH.OH-CH3. 

The  very  close  connection  existing  between  acetone  and  second- 
ary propyl  alcohol,  and  the  fact'  that  there  are  two  methyl 
groups  in  acetone,  make  it  appear  probable  that  there  are  also 
two  methyl  groups  in  secondary  propyl  alcohol,  as  represented 
in  the  above  equation.  On  the  other  hand,  the  easy  transfor- 
mation of  primary  propyl  alcohol  into  propionic  acid,  which  can 
be  shown  to  contain  ethyl,  shows  that  in  the  alcohol  ethyl  is 
present.  Therefore,  we  may  conclude  that  the  difference 
between  primary  and  secondary  propyl  alcohol  is  that  the 
former  is  an  ethyl  derivative  and  the  latter  a  di-methyl  deriva- 
tive of  methyl  alcohol,  as  represented  by  the  formulas  :  — 


|C 

c 


CH3 


H 
OH 

Ethyl  methyl  alcohol  or  Dimethyl  methyl  alco- 

ordinary  propyl  al-  hoi  or  secondary 

cohol.  propyl  alcohol. 

Primary  propyl  alcohol  is  methyl  alcohol  in  which  one  hydrogen 
is  replaced  by  a  radical,  while  secondary  propyl  alcohol  is 
methyl  alcohol  in  which  two  hydrogens  are  replaced  by  radicals. 
An  examination  of  all  secondary  alcohols  known  shows  that 
the  above  statement  may  be  made  in  regard  to  all  of  them. 
They  must  be  regarded  as  derived  from  methyl  alcohol  by  the 
replacement  of  two  hydrogen  atoms  by  radicals.  The  alcohols 
of  the  first  class,  like  methyl,  ethyl,  and  ordinary  propyl  alco- 
hols, which  are  derived  from  methyl  alcohol  by  the  replacement 
of  one  hydrogen  by  a  radical,  are  called  primary  alcohols. 
Another  way  of  stating  the  difference  between  primary  and 


BUTYL   ALCOHOLS.  123 

secondary  alcohols  is  this  :  Primary  alcohols  contain  the  group 
CH2OH  ;  secondary  alcohols  contain  the  group  CHOH.  These 
statements,  as  will  be  seen,  are  corollaries  of  the  first  ones. 

A  primary  alcohol,  when  oxidized,  yields  an  aldehyde  and  an 
acid  containing  the  same  number  of  carbon  atoms  as  the 
alcohol  does. 

A  secondary  alcohol,  when  oxidized,  yields  an  acetone,  and 
then  an  acid  or  acids  containing  a  smaller  number  of  carbon 
atoms. 

Recalling  what  was  said  regarding  the  nature  of  the  changes 
involved  in  passing  from  an  alcohol  to  the  corresponding  alde- 
hyde and  acid,  we  see  that  the  formation  of  the  acid  is  impossi- 
ble in  the  case  of  a  secondary  alcohol.  In  the  case  of  a 
primary  alcohol,  we  have  :  — 

rR  rR 

C  J  H  C  J  OH. 

lo  lo 

Aldehyde.  Acid. 

In  the  case  of  the  secondary  alcohol,  we  have :  — 

rR 

r    R  / 

UH  ^' 

Secondary  alcohol.  Ketone. 

Further  introduction  of  oxygen  cannot  take  place  without  a 
breaking  down  of  the  compound.  It  will  be  seen  that  the 
formulas  used  to  express  the  structure  of  the  compounds  are 
remarkably  in  accordance  with  the  facts. 

Butyl  alcohols,  C4H9.OH.  —  Theoretically,  there  are  two 
possible  hydroxyl  derivatives  of  each  of  the  two  butanes, 
making  four  butyl  alcohols  in  all.  They  are  all  known.  Two 
are  primary  alcohols. 


124  DERIVATIVES    OF    THE   PARAFFINS. 

1.  Normal  butyl  alcohol,  CH3.CH2.CH2.CH2.OH. 

2.  Isobutyl  alcohol,  ^3>CH.CH2OH. 


The  third  is  a  derivative  of  normal  butane,  and  is  a  secondary 
alcohol. 

OTT 

3,  Secondary  butyl  alcohol,  CH3.CH2.CH<  ^     •     This 

LH3 

alcohol  is  prepared  by  treating  ethyl-methyl  ketone  with  nascent 
hydrogen  :  — 

CH3.CH2-CO-CH3  +  H2  =  CH3.CH2.CH<°^ 

CH3 

(Compare  this  with  the  reaction  for  making  secondary  propyl 

alcohol.)  CH3 

I 

4.  Tertiary  butyl  alcohol,  CH3-C-OH.     The  fourth  butyl 

CH3 
alcohol  has  properties  which  distinguish  it  from  the  primary  and 

secondary  alcohols.  When  oxidized  it  yields  neither  an  alde- 
hyde nor  an  acetone,  but  breaks  down  at  once,  yielding  acids  con- 
taining a  smaller  number  of  carbon  atoms.  Assuming  that  ever}7 
primary  alcohol  contains  the  group  CH2OH,  and  that  every  sec- 
ondary alcohol  contains  the  group  CHOH,  it  follows  that  the  two 
primary  butyl  alcohols  and  secondary  butyl  alcohol  must  have 

the  formulas  above  assigned  to  them  ;  and  it  follows  further,  that 

CH3 

! 
the  fourth  butyl  alcohol  must  have  the  formula  CH3  —  C  —  OH, 

CH3 

as  this  represents  the  only  other  arrangement  of  the  constituents 
possible,  according  to  our  theory.  This  formula  represents  a 
condition  which  does  not  exist  in  either  the  primary  or  second- 
ary alcohols.  It  is  methyl  alcohol  in  which  all  the  hydrogen 
atoms,  except  that  in  the  hydroxyl,  are  replaced  by  methyl 
groups,  and  it  contains  the  group  C  —  (OH).  Such  an  alcohol 
is  known  as  a  tertiary  alcohol,  and  the  one  under  consideration 


PENTYL   ALCOHOLS.  125 

is  called  tertiary  butyl  alcohol.     It  is  the  simplest  derivative  of 
a  class  of  which  but  few  members  are  known. 

Tertiary  butyl  alcohol  is  made  by  a  complicated  reaction 
which  cannot  easily  be  interpreted;  viz.,  by  treating  acetyl 
chloride,  CH3.COC1,  with  zinc  methyl,  Zn(CH3)2.  These  two 
substances  unite,  forming  a  crystallized  compound ;  and,  when 
this  is  treated  with  water,  it  breaks  up,  yielding  several  products, 
among  which  is  tertiary  butyl  alcohol.  By  taking  other  acid 
chlorides,  and  the  zinc  compounds  of  other  radicals,  other 
tertiary  alcohols  may  be  obtained. 

Characteristics  of  the  three  Classes  of  Alcohols.  To  recapitu- 
late briefly,  we  find,  in  studying  the  hydroxyl  derivatives  of  the 
hydrocarbons,  that  they  can  be  divided  into  three  classes,  ac- 
cording to  their  conduct  towards  oxidizing  agents. 

To  what  was  said  above  regarding  the  conduct  of  primar}' 
and  secondary  alcohols  we  can  now  add :  Tertiary  alcohols 
yield  neither  aldehydes  nor  acetones,  but  break  down  at  once, 
yielding  simpler  acids. 

The  general  formulas  representing  these  three  kinds  of  alco- 
hols are :  — 


and 

Secondary. 


NOTE  FOR  STUDENT.  —  Show  how  the  formula  for  the  tertiary  alco- 
hols is  in  accordance  with  the  fact  that  these  alcohols  do  not  yield 
aldehydes  nor  ketones. 


Pen tyl  alcohols,  C5Hn.OH. — These  alcohols  are  the  hy- 
droxyl derivatives  of  the  pentanes.  Eight  are  possible,  and 
seven  of  these  are  known.  Only  two  of  them  need  be  con- 
sidered here.  These  are  the  so-called  amyl  alcohols. 


126  DERIVATIVES   OF   THE   PARAFFINS. 


Inactive    amyl    alcohol,       TT  >  CH  -  CH,  -  CHoOH.  — 

O±±3 

This  alcohol,  together  with  at  least  one  other  of  the  same 
composition,  forms  the  chief  part  of  the  fusel  oil  obtained  in 
the  fermentation  of  sugar.  By  fractional  distillation  of  fusel 
oil  ordinary  commercial  amyl  alcohol  is  obtained,  as  a  colorless 
liquid,  having  a  penetrating  odor,  and  boiling  at  131°  to  132°. 
This  can  be  separated  by  other  methods  into  two  isomeric 
alcohols,  one  of  which  is  inactive  amyl  alcohol  and  the  other 
active  amyl  alcohol.  The  names  refer  to  the  behavior  of  the 
substances  towards  polarized  light,  the  former  having  no  action 
upon  it,  the  latter  turning  the  plane  of  polarization1  to  the  left. 
When  oxidized,  inactive  amyl  alcohol  yields  an  acid  contain- 
ing the  same  number  of  carbon  atoms,  and  is,  therefore,  a 
primary  alcohol.  The  acid  has  been  made  by  simple  reac- 
tions which  show  that  it  must  be  represented  by  the  formula 

^H3>CH.CH2.CO2H.     Therefore,  the  alcohol  has  the  structure 

CH3  PTT 

represented  by  the  formula  ^3  >  CH.CH2.CH2OH. 


CH3         _, 


Active  amyl  alcohol,  CH3.CH2.CH<^OH.— This,  as 

has  been  stated,  is  obtained,  together  with  the  inactive  alcohol, 
from  fusel  oil.  Not  enough  is  known  about  it  to  enable  us  to 
say  with  certainty  whether  the  above  formula  represents  its 
structure  or  not.  It  is  a  primary  alcohol  as  represented. 

The  remaining  members  of  the  series  will  not  be  considered, 
though  a  list  of  some  of  the  more  important  ones  is  given 
below.  As  regards  the  naming  of  the  alcohols,  it  is  best  to 
refer  them  to  methyl  alcohol,  just  as  the  hydrocarbons  are 
referred  to  marsh  gas.  For  this  purpose  methyl  alcohol  is 
called  carbinol,  and  we  then  get  such  names  as  methyl-carbiuol, 
di-ethyl-carbinol,  etc.,  which  convey  at  once  an  accurate  idea 

1  This  is  not  the  proper  place  to  explain  exactly  what  is  meant  by  these  expressions. 
To  the  student  of  physics  they  convey  definite  meanings.  To  one  who  has  not  studied 
physics  they  are  meaningless. 


NOMENCLATURE.  127 

concerning  the  structure  of  the  substances.     A  few  illustrations 
will  suffice.     Take  the  alcohols  considered  above  :  — 


Ethyl  alcohol  is  methyl-carbinol, 


H 

Primary  propyl  alcohol  is  ethyl-carbinol,         C  «|  ; 

OH 

CH3 

Secondaiy   propyl   alcohol  is  di-methyl-  )     ^  J  CH3 
carbinol,  )         |  H 

OH 

CH3 

Tertiary  butyl  alcohol  is  tri-methyl-carbinol,  C  ^         3 ; 

OH 


Inactive  amyl  alcohol  is  isobutyl-carbinol,      C 

H 

OH,   etc.,  etc., 

a  name  given  to  it  on  account  of  the  presence  in  it  of  the  iso- 

i        i  CHo 

butyl  group  CH2.CH  <  CH  . 

The  following  table  will  give  an  imperfect  idea  of  the  extent 
to  which  the  series  of  alcohols  derived  from  the  paraffins  is 
developed.  There  are  eight  hexyl  alcohols  and  four  heptyl 
alcohols  known.  Of  most  of  the  higher  members  but  one 
variety  is  known.  They  are  not  important,  except  in  so  far 
as  they  indicate  the  possibility  of  the  discovery  of  other 
alcohols. 


128  DERIVATIVES   OF  THE  PARAFFINS. 

ALCOHOLS    OF   THE    METHYL   ALCOHOL  SERIES. 
SERIES  CnH2n+1.OH. 

Methyl  alcohol CH3.OH. 

Ethyl         "        C2H5.OH. 

Propyl       "        C3H7.OH. 

Butyl        " C4H9.OH. 

Pentyl       "        C5Hn.OH. 

Hexyl        " C6H13.OH. 

Heptyl      "        C7H15.OH. 

Octyl         "        C8H17.OH. 

Nonyl        "        C9H19.OH. 

Cetyl         " 

Ceryl         "        ......... 

Myricyl     "        

2.  ALDEHYDES. 

In  general,  it  follows  from  what  has  been  said  concerning 
the  properties  of  primary  alcohols,  that  there  should  be  an 
aldehyde  corresponding  to  every  primary  alcohol.  Many  of  these 
have  been  prepared.  They  resemble  ordinary  acetic  aldehyde  so 
closely  that  it  is  unnecessary  to  take  them  up  individually.  If 
we  know  the  structure  of  the  alcohol  from  which  an  aldehyde  is 
formed  by  oxidation,  we  also  know  the  structure  of  the  aldehyde. 

Besides  the  one  method  for  the  preparation  of  aldehydes 
which  has  been  mentioned,  viz.,  the  oxidation  of  primary 
alcohols,  there  is  one  other  which  should  be  specially  noticed. 
It  consists  in  distilling  a  mixture  of  a  formate  and  a  salt  of 
some  other  acid.  Thus,  if  a  mixture  of  an  acetate  and  a 
formate  be  distilled,  acetic  aldehyde  is  formed  as  represented 
by  the  equation  :  — 

-  CH°-COH  +  M'co°- 

Aldehyde. 


FATTY   ACIDS.  129 

This  method  has  been  used  to  a  considerable  extent  in  making 
the  higher  members  of  the  series. 

Experiment  32.  Mix  about  equal  weights  of  dry  potassium  form- 
ate and  dry  sodium  acetate.  Distil  from  a  small  flask.  Collect  some 
of  the  distillate  in  water,  and  prove  that  aldehyde  is  formed. 

3.  ACIDS. 

Formic  and  acetic  acids  are  the  first  two  members  of  an 
homologous  series  of  similar  acids,  generally  called  the  fatty 
adds,  on  account  of  the  fact  that  several  of  them  occur  in  large 
quantities  in  the  natural  fats.  The  names  and  formulas  of 
some  of  the  principal  members  are  given  in  the  following 
table.  The  reasons  for  representing  the  acids  as  compounds 
containing  the  carboxyl  group,  CO2H,  have  been  given,  and 
need  not  here  be  restated  :  — 

FATTY   ACIDS. 
SERIES  CnH2n+1  .CO2H,  or  CnH2nO2. 

Formic        acid H.CO2H. 

Acetic          " CH3.CO2H. 

Propionic     " C2H5.CO2H. 

Butyric         " C3H7.CO2H. 

Valeric         " C4H9.CO2H. 

Caproic  or 


„  -  C5HU.C02H. 

Hexoic  acids     ) 

OEnanthylic  or  \  p         pn 

TT      ,    .          .,       f C6H13.U<J2tl. 

Heptoic  acids   ) 

Caprylicor       )  r  TT     CO  TT 

n   .    .          .,         f Ujlliff  .UVfO.. 

(Jctoic  acids     ) 

Pelargonic  or    \ 
,T  ., 

JNonoic  acids     ) 

Capric        acid .      C9H19.CO2H. 


130  DERIVATIVES   OF   THE  PARAFFINS. 

Laurie     .  acid "...  CnH23.CO2H. 

Myristic      " C13Hx  .CO2H. 

Palmitic      " C15H31.CO2H. 

Margaric     " C^H^.CO^H- 

Stearic         " C^H^.COsH. 

Arachidic    " C^H^.CO^. 

Behenic       " C21H43.CO2H. 

Hyenic        " C24H49.CO2H. 

Cerotic         " C26H53.CO2H. 

Melissic       "  ... 


Although,  as  will  be  seen,  a  large  number  of  fatty  acids  are 
known,  most  of  them  included  in  the  list  are  at  present  merely 
curiosities,  and  need  not  be  studied  specially.  Not  more  than 
six  in  addition  to  formic  and  acetic  acids  will  require  attention. 

Propionic  acid,  C3H6O2(C2H5.CO2H).  —  Propionic  acid  is 
formed  in  small  quantity  by  the  distillation  of  wood,  and  by  the 
fermentation  of  various  organic  bodies,  particularly  calcium 
lactate  and  tartrate.  It  is  prepared  most  readily  by  treating 
ethyl  cyanide  (propio-nitrile)  with  caustic  potash  :  — 

C2H5.CN  +  KOH  +  H2O  =  C2H5.CO2K  +  NH3. 

Other  methods  for  preparing  it  are  the  following :  — 

(1)  By  reducing  lactic  acid  with  hydriodic  acid.     (This  will 
be  explained  under  the  head  of  Lactic  Acid,  which  see.) 

(2)  By  the  action  of  carbon  dioxide  upon  sodium  ethyl :  — 

CO2  +  NaC2H5  =  C2H5.CO2Na. 

It  is  a  colorless  liquid  with  a  penetrating  odor  somewhat  re- 
sembling that  of  acetic  acid.  It  boils  at  140°.  (Compare  with 
boiling-points  of  formic  and  acetic  acids.) 


PKOPIONIC   ACID.  131 

It  yields  a  large  number  of  derivatives  corresponding  to 
those  obtained  from  acetic  acid. 

NOTE  FOR  STUDENT.  —  What  is  propionyl  chloride?  and  how  can  it 
be  prepared?  It  is  analogous  to  acetyl  chloride. 

The  simple  substitution- products  of  propionic  acid  present  an 
interesting  and  instructive  case  of  isomerism.  It  is  found  that 
there  are  two  chlor-propiouic  acids,  two  brom-propionic  acids, 
etc.  Those  products  which  are  obtained  by  direct  treatment  of 
propionic  acid  with  substituting  agents  are  called  a-products, 
and  the  isomeric  substances  ^-products.  Thus  we  have  a-chlor- 
propionic  and  a-brom-propionic  add,  made  by  treating  propionic 
acid  with  chlorine  and  bromine  ;  and  f}-chlor-propionic  add  and 
/3-brom-propionic  add,  made  by  indirect  methods.  The  differ- 
ence between  these  two  series  of  derivatives  is  due  to  different 
relations  between  the  constituents.  Our  usual  method  of  repre- 
sentation indicates  the  possibility  of  the  existence  of  two  iso- 
meric chlor-propionic  acids,  and  of  similar  mono-substitution 
products  of  propionic  acid.  The  acid  is  represented  thus  :  — 

CH3.CH2.CO2H. 

Now,  if  chlorine  should  enter  into  the  compound,  as  represented 
by  the  formula  CH2C1  .CH2  .CO2H,  (1)  we  would  have  one  of 
the  chlor-propionic  acids  ;  while,  if  it  should  enter  as  indicated 
in  the  formula  CH3.CHC1.CO2H,  (2)  we  would  have  the  iso- 
meric product.  We  have  thus  two  chlor-propionic  acids  actu- 
ally known,  and  our  theory  gives  us  two  formulas.  How  can 
we  tell  which  of  the  formulas  represents  a-chlor-propionic  acid, 
and  which  the  /2-acid?  We  can  tell  only  by  carefully  consider- 
ing all  the  reactions  and  methods  of  formation  of  both  com- 
pounds. The  best  evidence  is  furnished  by  a  study  of  the  lactic 
acids,  which  will  be  shown  to  be  mono-substitution  products  of 
propionic  acid.  It  will  be  shown  that  a-chlor-propionic  acid 
can  be  transformed  into  a  lactic  acid  the  structure  of  which  is 
represented  by  the  formula  CH3.CH(OH).CO2H,  and  that,  by 


132  DERIVATIVES   OF   THE  PARAFFINS. 

replacing  the  hydroxyl  of  this  lactic  acid  by  chlorine,  u-chlor- 
propionic  acid  is  formed.  It  therefore  follows  that  formula  (2) 
above  given  is  that  of  a-chlor-propionic  acid,  and  formula  (1) 
that  of  /?-chlor-propionic  acid.  Further,  any  mono-substitution 
product  of  propionic  acid  which  can  be  made  directly  from 
a-chlor-propionic  acid,  or  converted  directly  into  this  acid,  is  an 
a-product,  and  has  the  general  formula 

CH3.CHX.CO2H; 

and,  similarly,  the  /^-products  have  the  general  formula 

CH2X.CH2.C02H, 
in  which  X  represents  any  univalent  atom  or  group. 

Butyric  acids,  C4H8O2(C3H7.CO2H). 

Normal  butyric  acid,  CH3.CH2.CH2.CO2H.  When  butter  is 
boiled  with  caustic  potash,  the  potassium  salts  of  butyric  acid  and 
of  some  of  the  higher  members  of  the  series  are  found  in  the  solu- 
tion at  the  end  of  the  operation.  Butter,  like  other  fats,  belongs 
to  the  class  of  bodies  known  as  ethereal  salts  ;  and  these,  as  we 
have  seen,  when  boiled  with  the  alkalies  are  decomposed,  yielding 
alcohol  and  alkali  salts  of  acids  (saponification) .  In  the  case  of 
butter  and  of  nearly  all  other  fats,  the  alcohol  formed  is  glycerin. 
Butyric  acid  occurs  also  in  many  other  fats  besides  butter. 

It  is  made  most  readily  by  fermentation  of  sugar  by  what  is 
known  as  the  butyric  acid  ferment.  This  ferment  probably  is 
contained  in  putrid  cheese.  Hence,  to  make  the  acid,  sugar 
and  tartaric  acid  are  dissolved  in  water,  and,  after  a  time, 
certain  quantities  of  putrid  cheese  and  sour  milk  are  added, 
and  also  some  powdered  chalk.  At  first  the  sugar  is  converted 
into  glucose  :  — 

C12H22On  +  H2O  ~  2  C6H12O6. 

Cane  sugar.  Glucose. 

The  glucose  breaks  up,  yielding  lactic  acid,  C3H6O8:  — 
C6H12Oe  =  2  C3H6O3. 

Glucose.  Lactic  acid. 


VALERIC   ACIDS.  133 

And,  finally,  the  lactic  acid  is  converted  into  butyric  acid :  — 
2  C3H603  =  C4H802  +  2  CO,,  +  4  H. 

Other  methods  for  the  preparation  of  but3*ric  acid  are :  — 

(1)  By  oxidation  of  normal  butyl  alcohol ;  and 

(2)  By  treating  normal  propyl  cyanide,  CH3.CH2.CH2CN. 
with  caustic  potash. 

The  acid  is  a  liquid  having  an  acid,  rancid  odor,  like  that  of 
rancid  butter.  It  boils  at  163°.  (Compare  with  the  preceding 
acids.)  Like  the  lower  members  of  the  series  it  mixes  with 
water  in  all  proportions. 

Ethyl  butyrate,  C3H7.CO2C2H5,  has  a  pleasant  odor  resembling 
that  of  pineapples.  It  is  used  under  the  name  of  essence  oj 


Isobutyric  acid,  3  >  CH.CO2H.  —  From  the  two  propyl 
alcohols  the  two  chlorides,  propyl  chloride,  CH3.CH2.CH2C1, 
and  isopropyl  chloride,  3  >  CHC1,  can  be  made,  and  from 

V/Xiq 

these  the  corresponding  cyanides,  — 

Propyl  cyanide    .     .     .     .     .     CH3.CH2.CH2CN, 

TT 

and      Isopropyl  cyanide    ... 


CH3 

By  boiling  with  caustic  potash,  the  former  is  converted  into 
normal  butyric  acid,  as  stated  above  ;  while  the  latter  yields 

/~1TT 

isobutyric  acid,       3>CH.CO2H.     This   acid   may  be   prepared 

tf^T-T 

also   by   oxidizing   isobutyl  alcohol,   ^3>  CH.CELOH.       It  is 

CH3 

found  in  nature  in  the  carob  bean. 

Isobutyric  acid  is  a  liquid  which  boils  at  154°.  Its  odor  is 
less  unpleasant  than  that  of  the  normal  acid. 

Valeric  acids,  C5H10O2(C4Hy.COoH).  —  Four  carboxyl  de- 
rivatives of  the  butanes  are  possible.  Four  acids  of  the 
formula  C5H10O2  are  known. 


134  DERIVATIVES   OF   THE   PARAFFINS. 


Inactive  or  ordinary  valeric  acid,  Q-g3  >  CH.CH2.CO2H. 

—  This  acid  is  made  by  oxidizing  inactive  amyl  alcohol.  It 
may  also  be  made  (and  this  reaction  reveals  the  structure  of 
the  acid)  by  starting  with  isobutyl  alcohol,  J^3>  CH.CH2OH, 

UH3 

converting  this  first  into  the  chloride  and  then  into  the  cyanide, 

/~ITT 

and,  finally,  transforming  the  cyanide,  which  is       3  >  CH.CH2CN, 

L/H3 

into  the  acid.  It  occurs  in  valerian  root,  whence  its  name.  It 
is  an  unpleasant  smelling  liquid,  boiling  at  175°.  It  requires 
thirty  parts  of  water  for  solution. 

Amyl  valerate,  C4H9  .  CO2C5Hn,  has  the  odor  of  apples,  and  is 
used  under  the  name  of  essence  of  apples. 


Active  valeric  acid,  QQ"  >  CH.CH2.CH3.  —  This  acid 
is  prepared  by  oxidation  of  active  amyl  alcohol.  Although  the 
alcohol  turns  the  plane  of  polarization  to  the  left,  the  acid 
turns  it  to  the  right.  The  alcohol  is  said  to  be  Icevo-rotatory  ', 
and  the  acid  dextro-rotatory. 


The  higher  acids  of  the  series  are,  for  the  most  part,  found 
in  various  fats.  They  are  difficultly  soluble  in  water.  The 
highest  members  are  solids.  The  two  best  known,  because 
occurring  in  largest  quantity,  are  palmitic  and  stearic  acids. 
These  are  contained  in  combination  with  the  alcohol,  glycerin,  in 
all  the  common  fats.  The  fats  will  be  treated  of  under  the 
head  of  Glycerin. 

Palmitic  acid,  C15H3i.CO2H,  maybe  made  by  saponifying 
many  fats,  but  especially  palm-oil,  from  which  it  is  obtained 
mixed  with  only  one  other  acid. 

It  crystallizes  in  needles  which  melt  at  62°. 


Stearic  acid,  CnH^.CC^H,  is  the  acid  contained  in  that 
particular  fat  known  as  stearin,.     The  so-called  "  stearin  can- 


SOAPS.  135 

dies "  are  really  made  of  a  mixture  of  palmitic  and  stearic 
acids,  and  from  them  stearic  acid  can  be  separated  in  pure  form 
by  long-continued  fractional  crystallization  from  ether  and 
alcohol. 

It  crystallizes  from  alcohol  in  needles  or  laminae  which  melt 
at  69°. 

Soaps.  —  In  speaking  of  the  decompositions  of  ethereal  salts 
by  boiling  with  alkalies,  it  was  stated  that  this  process  is 
called  saponification  because  it  is  best  exemplified  in  the  manu- 
facture of  soaps  from  fats.  The  fats  are  themselves  rather 
complicated  ethereal  salts.  When  they  are  boiled  with  an 
alkali,  as  caustic  soda,  the  alcohol  is  liberated,  and  the  alkali 
salts  of  the  acids  are  formed.  These  salts  are  the  soaps.  They 
are  in  solution  after  the  process  of  saponification  is  completed, 
and  may  be  separated  by  adding  a  solution  of  common  salt,  in 
which  they  are  insoluble. 

Experiment  33.  In  an  iron  pot  boil  about  100^  of  lard  with  a 
solution  of  caustic  soda  for  two  hours.  After  cooling,  add  a  strong 
solution  of  sodium  chloride.  The  soap  will  separate  and  rise  to  the 
top  of  the  solution,  where  it  will  finally  solidify.  Dissolve  some  of 
the  soap  thus  obtained  in  water,  and  filter.  Add  hydrochloric  acid, 
when  the  free  fatty  acids,  mainly  palmitic  and  stearic  acids,  will 
separate  as  solids,  which  will  rise  to  the  top.  The  hydrochloric  acid 
simply  decomposes  the  sodium  palmitate  and  stearate,  giving  free 
palmitic  and  stearic  acids  and  sodium  chlorides  :  — 

C15H31.C02Na  +  HC1  =  C15H31.CO2H  +  NaCl, 

Sodium  Palmitate.  Palmitic  Acid. 

and  C17H35.C02Na  +  HC1  =  C17H35.CO2H  +  NaCl. 

Sodium  Stearate.  Stearic  Acid. 


The  remaining  derivatives  of  the  higher  members  of  the 
paraffin  series  include  the  ethers,  ketones,  ethereal  salts, 
mercaptans,  sulphur  ethers,  sulphonic  acids,  cyanides  and 
isocyanides,  cyanates  and  isocyanates,  sulpho-cyanates  and 


136  DERIVATIVES   OF   THE  PAKAFFINS. 

iso-sulpho-cyanates,  substituted  ammonias  and  analogous  com- 
pounds, metal  derivatives,  and  nitro-derivatives. 

A  great  many  substances  belonging  to  these  classes,  and 
containing  residues  of  the  higher  hydrocarbons,  have  been  pre- 
pared and  studied  ;  but,  in  the  main,  they  so  closely  resemble 
the  simpler  substances  which  have  already  been  described  that 
we  would  gain  nothing  by  taking  them  up  here  individually. 
The  student,  however,  is  earnestly  advised  to  apply  the  princi- 
ples discussed  in  the  first  part  of  the  book  to  a  few  other  cases. 
Thus,  let  him  take  propane  and  butane,  and,  not  only  write  the 
formulas  of  the  derivatives  which  may  be  obtained  from  them, 
but,  above  all,  write  the  equations  representing  the  action  in- 
volved in  their  preparation,  and  the  transformations  of  which 
they  are  capable. 

POLYACID    ALCOHOLS    AND    POLYBASIC    ACIDS. 
1.  DI-ACID  ALCOHOLS. 

The  alcohols  thus  far  considered  are  of  the  simplest  kind. 
They  correspond  to  the  simplest  metallic  hydroxides,  as  potas- 
sium hydroxide,  KOH.  Just  as  these  simplest  metallic  hydrox- 
ides are  called  mon-acid  bases,  so  the  simplest  alcohols  are 
called  mon-acid  alcohols?  expressions  which  are  suggested  b}~ 
the  term  mono-basic  acid.  But,  as  is  well  known,  there  are 
metallic  hydroxides,  like  calcium  hydroxide,  Ca(OH)2,  barium 
hydroxide,  Ba(OH)2,  etc.,  which  contain  two  hydroxyls,  and 
are  hence  known  as  di-acid  bases;  and  so,  too,  there  are  di-acid 
alcohols  which  bear  to  the  mon-acid  alcohols  the  same  relation 
that  the  di-acid  bases  bear  to  the  mon-acid  bases.  Only  one 
alcohol  of  this  kind,  derived  from  the  paraffin  hydrocarbons,  is 
well  known. 

Bthylene  alcohol  or  glycol,  C2H6O2[C2HJOH)2].— Glycol 
is  made  by  starting  with  ethylene,  a  hydrocarbon  of  the  formula 

1  The  expression  monatomic  alcohols  is  used  by  some  writers,  but,  as  it  is  confusing, 
it  is  gradually  giving  way  to  the  more  rational  expression  above  used. 


ETHYLENE   ALCOHOL.  137 

C2H4.  When  this  is  brought  together  with  bromine,  the  two 
unite  directly,  forming  ethylene  bromide,  C2H4Br2.  By  replacing 
the  two  bromine  atoms  by  hydroxyl,  ethylene  alcohol  or  glycol 
is  formed. 

It  is  a  colorless,  inodorous,  somewhat  oily  liquid,  which  boils 
at  197.5°.  It  has  a  sweetish  taste,  and  is  hence  called  glycol 
(from  yXvKvs,  siueet)  .  Hence,  further,  the  other  alcohols  of 
this  series  are  also  called  glycols. 

The  derivatives  of  ethylene  alcohol  are  not  as  numerous  as 
those  of  the  better  known  members  of  the  methyl  alcohol  series, 
but  those  which  are  known  are  of  the  same  general  character. 
The  reactions  of  the  alcohol  are  the  same  as  those  of  the  mon- 
acid  alcohols,  but  it  presents  more  possibilities.  In  most  cases 
in  which  a  mon-acid  alcohol  yields  one  derivative,  ethylene 
alcohol  yields  two.  Thus,  with  sodium,  the  two  compounds, 

ONa  ONa 

sodium   glycol,    C2H4<OH  »  and  di-sodium  glycol,  C2H4 


can  be  formed  ;   from  these,  by  treating  with  ethyl  iodide,  the 

(~\r^  TT 

two  ethers,    etliyl-glycol  ether,  C2H4<     J<1   5,  and  di-ethyl-glycol 

OH 

ether,    C2H4<       2   5,    are    made.      By    treatment   with    hydro- 

25  Cl 

chloric  acid,  the  chloride,  C2H4<       ,  known  as  ethylene  chlor- 

hydrine  is  formed  ;  and  this,  by  treatment  with  phosphorus  tri- 
chloride, may  be  converted  into  ethylene  chloride,  C2H4C12,  etc. 
Its  conduct  towards  acids  is  like  that  of  a  di-acid  base.  It 
forms  neutral  and  alcoholic  salts,  of  which  the  acetates  may 
serve  as  examples.  Thus  we  have  the 


Mono-acetate,     24 

OH 


and  the  Di-acetate,       C2H4  < 


the  former  still  containing  alcoholic  hydroxyl  and  corresponding 
to  a  Dasic  salt  ;  the  latter  being  a  neutral  compound. 


138  DERIVATIVES    OF   THE   PARAFFINS. 

Under  the  head  of  Acetyl  Chloride  (see  p.  62)  the  action 
of  acetyl  chloride  upon  organic  compounds  containing  oxygen 
was  spoken  of  as  affording  a  convenient  method  of  determining 
whether  a  given  substance  is  an  alcohol  or  not.  It  is  plain 
that,  as  the  reaction  which  takes  place  between  a  mon-acid 
alcohol  and  acetyl  chloride,  and  which  is  represented  by  the 
equation 

R.OH  +  C2H3OC1  =  R.OC2H30  +  HC1, 

is  due  to  the  presence  of  alcoholic  hydroxyl,  the  reaction  must 
be  repeated  for  every  alcoholic  hydroxyl  contained  in  the  com- 
pound ;  or,  at  least,  this  result  would  be  expected.  As  a 
matter  of  fact  the  reaction  is  thus  repeated  for  every  alcoholic 
hydroxyl  present.  Hence,  by  treating  an  oxygen  derivative 
with  acetyl  chloride,  we  can  not  only  determine  whether  the 
derivative  is  an  alcohol  or  not,  but  also,  if  it  is  an  alcohol, 
whether  it  is  mon-acid  or  di-acid,  etc.  Thus,  suppose  we 
treat  ethylene  alcohol  with  acetyl  chloride.  This  reaction  takes 
place,  — 

C2H4(OH)2  +  2  C2H3OC1  =  C2H4<°^H30  +  2  HC1 ; 

UL2rl3U 

and  a  bocty,  which  analysis  shows  to  have  the  composition  repre- 
sented by  the  formula 


is  formed.  Such  a  body  could  only  be  formed  by  the  introduc- 
tion of  two  acet}Tl  groups  into  the  alcohol,  and  we  therefore 
conclude  that  the  original  substance  is  a  di-acid  alcohol. 

There  are  two  ways  in  which  the  structure  of  a  compound 
of  the  formula  C2H4(OH)2  may  be    represented.      They  are, — 

CH2(OH) 
(1)     I  ,  in  which  each  hydroxyl  is  represented  in  combi- 

CH,(OH)  CH(OH), 

nation  with  a  different  carbon  atom  ;  and  (2)    I  ,  in  which 

CHS 
both  hydroxyls  are  represented  in  combination  with  the  same 


ETHYLENE   ALCOHOL,  139 

carbon  atom.  The  question  at  once  suggests  itself,  to  which  of 
these  formulas  does  ethylene  alcohol  correspond?  To  answer 
this  question,  we  must  recall  what  was  said  regarding  the  two 
dichlor-ethanes,  known  as  ethylene  chloride  and  ethylidene  chloride. 
The  former  of  these  corresponds  to  the  formula  CH2C1.CH2C1, 
while  the  latter,  which  is  formed  from  aldehyde  b}*  replacing  the 
carbonyl  oxygen  by  two  chlorine  atoms,  is  represented  by  the 
formula  CHC12.CH3.  When  the  chlorine  atoms  of  ethylene 
chloride  are  replaced  by  hydroxyl,  ethylene  alcohol  is  produced. 

CH2(OH) 
Hence,  the  alcohol  has  the  formula    I  ,  or  each  of  the 

CH2(OH) 

hydroxyls  is  in  combination  with  a  different  carbon  atom. 

All  attempts  to  make  the  isomeric  di-acid  alcohol  correspond- 
ing to  eth}'lidene  chloride,  and  having  both  Irvdroxyls  in  combi- 
nation with  the  same  carbon  atom,  as  represented  in  the  formula 
CH(OH2) 

I  ,  have  failed.     Instead  of  getting  ethylidene  alcohol, 

CH3 

aldehyde  is  generally  obtained.  Aldehyde  is  ethylidene  alcohol 
minus  water :  — 

CH(OH)o       CHO 

I  =    I        4-  H20. 

CH3  CH3 

It  is  believed  that  one  carbon  atom  cannot,  under  ordinary 
circumstances,  hold  in  combination  more  than  one  hydroxyl 
group.  If  this  is  true,  then  ethylidene  alcohol  cannot  be  pre- 
pared any  more  than  our  hypothetical  carbonic  acid,  CO  <  ^H, 

OH 

can  be.  So,  too,  the  simplest  di-acid  alcohol  conceivable, 
viz.,  methylene  alcohol,  CH2(OH)2,  cannot  exist,  but  would 
break  up,  if  formed  at  all,  into  water  and  formic  aldehyde :  — 

CH2(OH)2=  H2O  +  H.CHO. 

(See  discussion  regarding  the  transformation  of  alcohol  into 
aldehyde,  pp.  64-66.) 


140  DERIVATIVES    OF   THE   PARAFFINS. 

Ethyl  alcohol,  as  was  pointed  out,  may  be  regarded  either  as 
ethane  in  which  one  hydrogen  is  replaced  by  hydroxyl,  or  as 
water  in  which  one  hydrogen  is  replaced  by  the  radical  C2H5,  or 
ethyl.  Ethyl,  like  all  the  radicals  contained  in  the  mon-acid 
alcohols,  is  univalent.  It  is  ethane  less  one  atom  of  hydrogen, 
just  as  methyl  is  methane  less  one  atom  of  hydrogen.  Each 
has  the  power  of  uniting  with  one  atom  of  hydrogen,  or  another 
univalent  element,  or  of  taking  the  place  of  one  atom  of 
hydrogen. 

If  we  take  away  two  atoms  of  hydrogen  from  methane  and 
ethane,  we  have  left  the  residues  or  radicals  CH2  and  C2H4. 
These  can  unite  with  two  atoms  of  hydrogen,  or  take  the  place 
of  two  atoms  of  hydrogen,  and  they  are  hence  called  bivalent 
radicals. 

Just  as  ethylene  alcohol  may  be  regarded  as  ethane  in  which 
two  hydrogen  atoms  are  replaced  by  hydroxyls,  so  it  may  be 
regarded  as  water  in  which  the  bivalent  radical  ethylene  re- 
places two  hydrogens  belonging  to  two  different  molecules  of 
water :  — 

0<H  0<H 

O  <  C2H< 

°<H  ^H 

Two  molecules  water.  Ethylene  alcohol. 


The  higher  members  of  the  series  of  di-acid  alcohols  will  not 
be  considered  here. 

2.  DIBASIC  ACIDS. 

Just  as  there  are  di-acid  alcohols  derived  from  the  paraffins, 
so  there  are  dibasic  acids  which  may  also  be  regarded  as  deriva- 
tives of  the  paraffins.  We  have  seen  that  the  simplest  acids, 
the  monobasic  fatty  acids,  are  closely  related  to  formic  and 
carbonic  acids  ;  that  they  may  be  regarded  as  derived  from  the 
latter  by  replacement  of  a  hydroxyl  by  a  radical,  or  as  derived 


DIBASIC   ACIDS.  141 

from  the  paraffins  by  the  introduction  of  the  group  carboxyl, 
CO2H.  The  conditions  existing  in  this  group  are  essential  to 
the  acid  properties.  If  two  carboxyls  be  introduced  into  marsh 
gas,  we  would  have  a  substance  of  the  formula  CH2(CO2H)2, 
and  this  is  a  dibasic  acid.  It  contains  two  acid  hydrogens,  and 
is  capable  of  forming  two  series  of  salts,  the  acid  and  neutral 
salts,  like  other  dibasic  acids.  It  may  be  regarded  also  as 
derived  from  two  molecules  of  carbonic  acid  by  the  replacement 
of  two  hydroxyls  by  the  bivalent  radical  CH2  :  — 

CO<M  C0<™ 

co<« 


Two  molecules  carbonic  acid.  Dibasic  acid. 

The  general  methods  of  preparation  available  for  the  building 
up  of  the  series  of  dibasic  acids  are  modifications  of  those  used 
in  making  the  monobasic  acids.  They  are  :  — 

1.  Oxidation  of  di-acid  primary  alcohols.      Just  as  a  mon- 
acid  primary  alcohol,  R.CH2OH,  yields  by  oxidation  a  mono- 
basic acid,  so  a  di-acid  primary  alcohol,  R"(CH2OH)2,  yields  a 
dibasic  acid,  R"(CO2H)2. 

2.  Treatment  of  the  dicyanides,  R"(CN)2,  with  caustic  alkalies. 

3.  Oxidation  of  the  so-called  Jiydroxy  -acids  or  alcohol  acids. 
These  are  compounds  which  are  at  the  same  time  alcohol  and 
acid  ;  as,  for  example,  hydroxy-acetic  acid,  which  is  acetic  acid 
in  which  one  of  the  hydrogen  atoms  of  the  hydrocarbon  residue, 
methyl,  has  been  replaced  by  hydroxyl,  as  represented  in  the 

CH2OH 

formula   I  .     When  this  is  oxidized,  the  alcoholic  portion, 

C02H 

CH2OH,  is  converted  into  carboxyl,  and  a  dibasic  acid  is  formed. 

4.  From  the  cyanogen  derivatives  of   the  monobasic  acids, 

ON 

such  as  cyan-acetic  acid,  CH2  <          ,  by  the  transformation  of 

v>  w^-H- 

the  cyanogen  group  into  carboxyl. 


142  DERIVATIVES   OF   THE   PARAFFINS. 

DIBASIC    ACIDS,    CnH2ll  204. 

Oxalic            acid (CO2H)2. 

Malonic            " CH,(CO2H)2. 

Succinic           " C2H4(CO2H)2. 

Pyrotartaric     " C3H6(CO2H)2. 

Adipic             " C4H8(CO2H)2. 

Pimelic             " C5H10(CO2H)2. 

Suberic            " C6H12(CO2H)2. 

Azelaic            " C7H14(CO2H)2. 

Sebacic            " C8H16(CO2H)2. 

Brassylic         .." C9H18(CO2H)2. 

Roccellic          " 


Of  the  many  acids  included  in  this  list  only  four  or  five  can 
be  said  to  be  well  known.  We  may  confine  our  attention  to  the 
first  four  members. 


Oxalic  acid,  GtHtO^GOfH)*].  —  In  one  sense,  according  to 
the  accepted  definition,  oxalic  acid  is  not  a  member  of  the  series 
with  which  we  are  dealing,  as  it  is  not  derived  from  a  hydro- 
carbon by  replacement  of  hydrogen  by  carboxyl  ;  nor  is  it 
derived  from  two  molecules  of  carbonic  acid  by  replacement  of 
two  hydroxyls  by  a  bivalent  radical.  Still  it  is  in  other  respects 
so  closely  allied  to  the  members  of  the  series,  and  has  so  many 
things  in  common  with  the  other  members,  that  it  would  be  a 
mere  act  of  pedantry  to  consider  it  in  any  other  connection. 

Oxalic  acid  occurs  very  widely  distributed  in  Nature  ;  as  in 
certain  plants  of  the  oxalis  varieties,  in  the  form  of  the  acid 
potassium  salt  ;  as  calcium  salt  in  many  plants  ;  in  urinary 
calculi  ;  and  as  the  ammonium  salt  in  guano. 

It  is  formed  by  the  action  of  nitric  acid  upon  many  organic 


OXALIC   ACID.  143 

substances,  particularly  the  different  varieties  of  sugar  and  the 
so-called  carbohydrates,  such  as  starch,  cellulose,  etc. 

Experiment  34.  In  a  good-sized  flask  pour  half  a  litre  of  ordinary 
concentrated  nitric  acid  (of  specific  gravity  1.245)  upon  50^  of  sugar. 
Heat  gently  until  the  reaction  begins.  Then  withdraw  the  flame,  when 
the  oxidation  will  proceed  with  some  violence,  and  accompanied  by 
a  copious  evolution  of  red  fumes.  When  the  action  has  ceased, 
evaporate  the  liquid  to  one-sixth  the  original  volume,  and  let  it 
cool,  when  oxalic  acid  will  crystallize  out.  Recrystallize  from  water 
the  acid  thus  obtained,  and  with  the  pure  substance  perform  such  ex- 
periments as  will  exhibit  its  properties.  For  example,  (1)  Heat  a 
specimen  at  100°,  and  notice  loss  of  water;  (2)  Heat  some  in  a  small 
flask  with  sulphuric  acid,  and  prove  that  both  oxides  of  carbon  are 
formed. 

On  the  large  scale,  oxalic  acid  is  made  by  heating  wood 
shavings  or  saw-dust  with  caustic  potash  and  caustic  soda  to 
240°  to  250°.  The  mass  is  extracted  with  water,  and  the  solu- 
tion evaporated  to  crystallization,  when  sodium  oxalate  is  de- 
posited. 

Other  methods,  which  are  interesting  from  a  purely  scientific 
stand-point,  are  the  following  :  — 

1.  The  spontaneous  transformation  of  an  aqueous  solution  of 
cyanogen :  — 

CN  C02H 

|      +4H20=    |          +    2NH3; 
CN  CO2H 

CN  CO2(NH4) 

or,  really,  |      +  4  H2O  =    | 

CN  CO2(NH4) 

2.  Treatment  of  carbon  dioxide  with  sodium :  — 

2  CO2  +  2  Na  =  C2O4Na2. 

3.  Heating  sodium  formate  :  — 

2H.CO2Na  =  C2O4Na2  +  2  H. 
Oxalic  acid  crystallizes  from  water  in  monoclinic  prisms  con- 


144  DERIVATIVES   OF   THE  PARAFFINS. 

taining  two  molecules  of  water  (C2H2O4  -f  2  H2O) .  It  loses 
this  water  at  100°.  It  sublimes  without  decomposition  at  150° 
to  160°,  but,  if  heated  higher,  it  breaks  up  into  carbon  monox- 
ide, carbon  dioxide,  and  formic  acid  :  — 

2  C2H2O4  =  2  CO2  +  CO   +  HCO2H  +  H2O. 

Sulphuric  acid  decomposes  it  into  carbon  monoxide,  carbon 
dioxide,  and  water.  Heated  with  glycerin  to  100°,  carbon 
dioxide  and  formic  acid  are  formed  (see  Formic  Acid)  :  — 

C2H2O4  =  CO2  +  H.CO2H. 

It  is  an  excellent  reducing  agent,  and  is  used  as  a  standardize! 
in  preparing  solutions  of  potassium  permanganate. 

Experiment  35.  Try  the  action  of  a  solution  of  potassium  per- 
manganate on  a  solution  of  oxalic  acid.  Why  is  it  best  to  have  the 
solution  of  the  permanganate  acid? 

Oxalic  acid  is  an  active  poison.     It  is  used  in  calico  printing. 

/Salts  of  oxalic  acid.  Like  all  bibasic  acids,  oxalic  acid  forms 
acid  and  neutral  salts  with  metals.  All  the  salts  are  insoluble 
except  those  containing  the  alkalies.  Among  those  most  com- 
mon are  the  acid  potassium  salt,  C2O4HK,  which  is  found  in  the 
sorrels  or  plants  of  the  oxalis  variety ;  the  ammonium  salt, 
C2O4(NH4)2,  of  which  some  urinary  calculi  are  formed ;  and 
calcium  oxalate,  C2O4Ca,  which,  being  insoluble  in  water  and 
acetic  acid,  is  used  as  a  means  of  detecting  calcium  in  the 
presence  of  magnesium. 

Malonic  acid,  C3H4O4[=  CH2(CO2H)2].— This  acid  was  first 
made  by  oxidation  of  malic  acid  (which  see),  and  is  hence 
called  malonic  acid.  It  can  best  be  made  by  starting  with 
acetic  acid.  The  necessary  steps  are:  (1)  making  chlor-acetic 
acid ;  (2)  transforming  chlor-acetic  acid  into  cyan-acetic  acid ; 
(3)  heating  cyan-acetic  acid  with  an  alkali. 

NOTE  FOR  STUDENT.  —  Write  the  equations  representing  the  three 
steps  mentioned. 


SUCCINIC   ACIDS.  145 

It  is  a  solid  which  crystallizes  in  laminae.  It  breaks  up  at  a 
temperature  above  132°,  which  is  its  melting-point,  into  carbon 
dioxide  and  acetic  acid  :  — 

2^  =  CH3.C02H  +  C02. 
(j2ti. 

NOTE  FOR  STUDENT.  —  What  simple  method  for  the  preparation  of 
marsh  gas  and  other  paraffins  is  this  reaction  analogous  to? 

Succinic  acids,  C4HfiO4[=  C2H4(CO2H)2].  —  Considering 
these  acids  as  derived  from  ethane  by  replacing  two  hydrogens 
with  carboxyl,  we  see  that  there  may  be  two  corresponding  to 
ethylene  and  ethylidene  chlorides.  Two  are  actually  known. 
One  is  the  well-known  succinic  acid ;  the  other  is  called  iso- 
succinic  acid. 

CH2.CO2H 

Succinic  acid,  Ethylene  succinic  acid,    I  . — 

CH2.CO2H 

This  acid  occurs  in  amber  (hence  its  name,  from  Lat.  sucdnum, 
amber)  ;  in  some  varieties  of  lignite ;  in  many  plants  ;  and  in 
the  animal  organism,  as  in  the  urine  of  the  horse,  goat,  and 
rabbit. 

It  is  formed  under  many  circumstances,  especially  by  oxida- 
tion of  fats  with  nitric  acid,  by  fermentation  of  calcium  malate, 
and,  in  small  quantity,  in  the  alcoholic  fermentation  of  sugar. 
Among  the  methods  for  its  preparation  are  :  — 

CH2.CN 

1.  Treatment  of  ethylene  cyanide,  |  ,  with  a  caustic 
alkali:—                                                   CH2.CN 

CH2CN  CH2.CO2K 

|  +  2  KOH  +  2  H2O  =   I  +  2  NH3. 

CH2CN  CH2.C02K 

2.  Similarly,  by  treatment  of  /?-cyan-propionic  acid  with  an 
alkali.      (What  is  /2-cyan-propionic  acid?) 

3.  Reduction   of    tartaric    and    malic    acids   by    means   of 


146  DERIVATIVES    OF   THE   PARAFFINS. 

hydriodic  acid.  These  well-known  acids  will  be  shown  to  be 
closely  related  to  succinic  acid,  and  the  reaction  here  mentioned 
will  be  explained.  The  methods  actually  used  in  the  prepara- 
tion of  succinic  acid  are:  (1)  the  distillation  of  amber,  and 
(2)  the  fermentation  of  calcium  malate. 

The  acid  crystallizes  in  monoclinic  prisms,  which  melt  at 
180°  (try  it).  It  boils  at  235°,  at  the  same  time  giving  off 
water,  and  being  converted  into  the  anhydride  :  — 


Among  the  salts  ferric  sucdnate,  C4H4O4.Fe(OH),  is  of 
special  interest,  as  it  is  entirely  insoluble  in  water,  and  may 
therefore  be  used  for  the  purpose  of  separating  iron  from 
manganese  quantitatively. 

Experiment  36.  Make  a  neutral  solution  of  ammonium  succinate 
by  neutralizing  an  aqueous  solution  of  the  acid,  and  boiling  off  all 
excess  of  ammonia.  Add  some  of  this  solution  to  a  solution  known  to 
contain  manganese  and  iron  in  the  ferric  state.  A  brown-red  precipi- 
tate will  be  formed.  Filter  and  wash,  and  examine  the  filtrate  for  iron. 

CH(C02H)2 
Isosuccinic  acid,  Bthylidene  succinic  acid,   I 

CH3 
This   acid  is  made  b}T  treating  a-cyan-propionic  acid  with  an 

alkali.     (What  is  a-cyan-propionic  acid?) 

Isosuccinic  acid  forms  crystals  which  melt  at  130°.  Heated 
to  150°  it  breaks  up  into  propionic  acid  and  carbon  dioxide  :  — 

CH(CO2H)2       CH2.CO2H 
I  =1  +  C02. 

CH3  CH3 

Isosuccinic  acid.  Propionic  acid. 

NOTE  FOR  STUDENT.  —  Notice  carefully  the  difference  between  the 
two  succiuic  acids,  as  shown  by  their  conduct  when  heated.  "What  is 
the  difference? 

Acids  of  the  formula  C5H8O4[=  C3H3(CO2H)2].  —  Four 
acids  of  the  formula  C5H8O4  are  known,  only  one  of  which, 
however,  need  be  considered  here.  This  is,  — 


GLYCERIN.  147 

CH3.CH.CO,H 

Pyrotartartic  acid,  I  •  —  As  the  name  mcb- 

CH,.CO2H 

cates,  this  acid  is  made  by  heating  tartaric  acid.  The  reactions 
which  take  place  are  complicated,  and  cannot  well  be  represented 
by  equations.  The  reactions  which  point  to  the  above  formula 
are  also  comparatively  complicated,  and  their  discussion  at  this 
time  would  tend  only  to  confuse  the  student. 


TRI-ACID  ALCOHOLS. 

The  existence  of  mon-acid  alcohols  corresponding  to  the 
mon-acid  bases,  like  potassium  hydroxide,  and  of  di-acid  alco- 
hols corresponding  to  the  di-acid  bases,  like  calcium  hydroxide, 
suggests  the  possible  existence  of  tri-acid  alcohols  correspond- 
ing to  tri-acid  bases,  like  ferric  hydroxide.  There  is  only  one 
alcohol  of  this  kind  derived  from  the  paraffin  hydrocarbons  that 
is  at  all  well  known.  This  is  the  common  substance  glycerin. 

Glycerin,  C3H8O3.  —  As  has  been  stated  repeatedly,  glycerin 
occurs  very  widely  distributed  as  the  alcoholic  or  basic  constit- 
uent of  the  fats.  The  acids  with  which  it  is  in  combination  are 
mostly  members  of  the  fatty  acid  series,  though  one,  viz.,  ole'ic 
acid,  which  is  found  frequently,  is  a  member  of  another  series. 
Besides  olei'c  acid,  the  two  acids  most  frequently  met  with  in 
fats  are  palmitic  and  stearic  acids.  When  a  fat  is  saponified 
with  caustic  potash,  it  yields  free  glycerin  and  the  potassium 
salts  of  the  acids.  The  reactions  in  the  case  of  the  glycerin 
compounds  of  palmitic  and  stearic  acids  are  these  :  — 

Formation. 

rOH       HO.OC.C15H31  (O.CO.C15H31 

C3HJ  OH  +  HO.OC.C15H31  =  C3HJ  O.CO.C^  +  3  H2O. 
(OH       HO.OC.dH!  (O.CO.CH 


O.CO.C15H31 

Glycerin.  Palmitic  acid. 


148  DERIVATIVES    OF   THE  PARAFFINS. 

r  OH       HO.OC.C^H^  r  O.OC.C17H35 

C3H5]  OH  +  HO.OC.CtfH,,,,  =  C3H5    O.OC.Cy^  +  3  H2O. 
(OH       HO.OC.C17H35 

Glycerin.  Stearic  Acid.  G 


Saponification. 

rO.OC.C15H31 
C3HJ  O.OC.C15H31  +  3KOH  =  C3H5(OH)3  +  3C15H31.CO2K. 

V.O.OC.C15H31  Glycerin.  Potassium  palmitate. 

Palmitin. 

rO.OC.CffH« 

C3HJ  O.OC.C17H«  +  3KOH  =  C3H5(OH)3  +  3  C^H^.CO.K. 

(.O.OC.CtfHgg  Glycerin.  Potassium  stearate. 

Stearin. 

The  fats  are  also  decomposed  by  superheated  steam,  yielding 
free  glycerin  and  the  free  acids,  and  this  method  is  used  on  the 
large  scale,  a  little  lime  being  added  to  facilitate  the  process. 
Lead  oxide  decomposes  fats  yielding  a  mixture  of  glycerin  and 
the  lead  salts  of  the  acids.  The  mixture  is  known  in  medicine 
as  "  lead  plaster." 

Glycerin  is  formed  in  small  quantity  by  the  alcoholic  fermen- 
tation of  sugar. 

It  has  been  made  synthetically  from  propylene  chloride, 
C3H6C12.  The  necessary  steps  are  :  (1)  treatment  with  chlorine, 
giving  C3H5C13  ;  (2)  treatment  of  the  tri-chlorine  derivative 
with  water,  thus  replacing  the  three  chlorine  atoms  by  hydroxyl. 

Glycerin  is  a  thick  colorless  liquid,  with  a  sweetish  taste 
(compare  with  glycol).  It  mixes  with  alcohol  and  water  in  all 
proportions.  It  attracts  moisture  from  the  air.  At  low  tem- 
peratures it  solidifies,  forming  deliquescent  crystals  which  melt 
at  17°.  Under  diminished  pressure  it  can  be  distilled;  but,  if 
heated  to  its  boiling-point  under  the  ordinary  atmospheric  pres- 
sure it  undergoes  decomposition.  It  is  volatile  with  water 
vapor. 


GLYCEKIN.  149 

Experiment  37.  Heat  a  little  glycerin  in  a  dry  vessel,  and  try  to 
boil  it.  What  evidence  have  you  that  it  undergoes  decomposition? 
Put  20CC  to  30CC  glycerin  in  400CC  to  500CC  water  in  a  flask;  connect  with 
a  condenser,  and  boil.  Prove  that  glycerin  passes  over  with  the  water 
vapor. 

The  reactions  of  glycerin  all  clearly  lead  to  the  conclusion 
that  it  is  a  tri-acid  alcohol. 

(1)  The  three  hydroxyl  groups  can  be  replaced  successively 
by  chlorine,  giving  the  compounds,  — 

5C1 
(OH)  ' 

DMdorhydrin,    C3H5  j  ^  ; 

and  Trichlorhydrin,  C3H5C13, 

which  last  compound  is  propane  in  which  three  hydrogen  atoms 

are  replaced  by  chlorine,  or  trichlorpropane. 

(2)  It  forms  three  classes  of  ethereal  salts  containing  one, 
two,  and  three  acid  residues  respectively.     For  example,  with 
acetyl  chloride  these  reactions  take  place :  — 

rOH  rO.C2H3O 

1.  C3H5]  OH  +  C2H3O.C1  =  C3H5]  OH       +  HC1. 

(OH  (.OH 

rOH  rOC2H3O 

2.  C3H5]  OH  +  2  C2H3OC1  =  C3H5]  OC2H3O  +  2  HC1. 

(OH  (OH 

rOH  rOC2H3O 

3.  C3H5]  OH  +  3  C2H3OC1  =  C3H.J  OC2H3O  +  3  HC1. 

(OH  (oc2H3o 

In  regard  to  the  relations  of  the  hydroxyl  groups  to  the  parts 

of  the  radical  C3H5,  we  have  very  little  experimental  evidence, 

though   it   appears   highly   probable   that  each  hydroxyl   is  in 

combination  with  a  different  carbon  atom  as  represented  in  the 

CH2OH 

formula  CHOH  . 

! 


150  DERIVATIVES    OF   THE   PARAFFINS. 

In  the  first  place,  we  have  seen  above  that  compounds  con- 
taining two  hydroxyls  in  combination  with  the  same  carbon 
are  not  readily  formed,  if  they  are  formed  at  all,  and  we  have 
had  some  reason  for  concluding  that  this  kind  of  combination 
is  impossible.  It  would  follow  from  this  that  the  simplest  tri- 
acid  alcohol  must  contain  at  least  three  atoms  of  carbon,  just 
as  the  simplest  di-acid  alcohol  must  contain  at  least  two  atoms 
of  carbon.  We  have  seen  that  the  simplest  tri-acid  alcohol 
known  does  contain  three  atoms  of  carbon. 

CH2OH 

Further,  if  the  formula  of  glycerin  is  CHOH  ,  it  contains   two 

CH2OH 

primary  alcohol  groups,  CH2OH,  and  we  have  seen  that  this 
group  is  converted  into  carboxyl  under  the  influence  of  oxidiz- 
ing agents.  Therefore,  we  would  expect  by  oxidizing  glycerin 

C02H  CO2H 

to  get  products  of  the  formulas,  CHOH  ,  and  CHOH.    Such  prod- 

CH2OH  C02H 

ucts  actually  are  obtained,  the  first  being  glyceric  add  (which 
see),  and  the  second  tartronic  add  (which  see). 

Just  as  ethyl  alcohol   is   regarded  as  water   in   which   one 

C*  TT    ) 

hydrogen  is  replaced  by  the  univalent  radical  C2H5,  as    2   5  [  O  ; 

H   ) 

and  glycol  is  regarded  as  water  in  which  two  hydrogen  atoms 
of  two  molecules  of  water  are  replaced  by  the  bivalent  radical 

H  >  O 
C2H4,  as  C2H4         ;  so  also  glycerin  may  be  regarded  as  water 

H  < 

in  which  three  hydrogen  atoms  of  three  molecules  are  replaced 
by  the  trivalent  radical  C3H5,  thus  :  — 

H.OH  rOH 

H.OH  C3H5]OH. 

H.OH  (OH 

Three  molecules  water.  Glycerin. 


BUTTER.  151 

Ethereal  salts  of  glycerin.  —  Among  the  important 
ethereal  salts  of  glycerin  are  the  nitrates.  Two  of  these  are 

rO.NOj 
known  ;  viz.,  the  mono-nitrate,  C3H5^  OH      ,  and  the  tri-nitrate, 

I  OH 

C3H5(ONO2)3,  the  latter  being  the  chief  constituent  of  nitro- 
glycerin.  Nitre-glycerin  is  prepared  by  treating  glycerin  with 
a  mixture  of  concentrated  sulphuric  and  nitric  acids.  It  is  a 
pale  yellow  oil  which  is  insoluble  in  water.  At  —20°  it 
crystallizes  in  long  needles.  It  explodes  very  violently  by 
concussion.  It  may  be  burned  in  an  open  vessel,  but  if  heated 
above  250°  it  explodes.  Dynamite  is  infusorial  earth  impreg- 
nated with  nitre-glycerin.  Nitre-glycerin  is  the  active  constitu- 
ent of  a  number  of  explosives. 

Fats.  —  The  relation  of  the  fats  to  glycerin  has  already  been 
stated.  Here  it  will  be  necessary  only  to  mention  the  composi- 
tion and  characteristics  of  some  of  the  more  common  fats. 

Most  fats  are  mixtures  of  the  three  neutral  ethereal  salts 
which  glycerin  forms  with  palmitic,  stearic,  and  ole'ic  acids, 
and  which  are  known  by  the  names  palmitin,  stearin,  and  ole'in. 
Ole'in  is  liquid,  and  the  other  two  fats  are  solids,  stearin  having 
the  higher  melting-point.  Therefore,  the  larger  the  proportion 
of  ole'in  contained  in  a  fat  the  softer  it  is,  while  the  greater  the 
proportion  of  stearin  the  higher  its  melting-point.  Among  the 
fats  which  are  particularly  rich  in  stearin  may  be  mentioned 
mutton  tallow,  beef  tallow,  and  lard.  Human  fat  and  palm  oil 
are  particularly  rich  in  palmitin.  Sperm  oil  and  cod-liver  oil 
are  rich  in  ole'in. 

Butter  consists  of  ethereal  salts  of  glycerin  and  the  follow- 
iug  acids  :  myristic,  palmitic,  and  stearic  acids,  which  are  not 
volatile,  and  butyric,  caproi'c,  caprylic,  and  capric  acids,  which 
are  volatile  with  water  vapors.  All  the  acids  mentioned  are 
members  of  the  fatty  acid  series.  Some  of  these  acids  are 
soluble  and  some  are  insoluble  in  water.  The  percentage  of 


152  DERIVATIVES    OF   THE  PARAFFINS. 

insoluble  fatty  acids  contained  in  butter  has  been  found  to  b<> 
88  per  cent.  As  the  proportion  of  insoluble  fatty  acids  con- 
tained in  artificial  butters,  such  as  the  so-called  oleo-margarin, 
is  greater  than  that  contained  in  butter,  it  is  not  a  difficult 
matter  to  distinguish  between  the  two  by  determining  the 
amount  of  these  acids  contained  in  them. 

TRI-BASIC  ACIDS. 

There  is  but  one  acid  to  be  considered  under  this  head.  It 
is, — 

Tri-carballylic  acid,  C3H5(CO2H)3.  —  This  acid  may  be 
made  from  trichlorhydrin,  C3H5C13  (which  see),  by  replacing 
the  chlorine  by  cyanogen,  and  heating  the  tricyanhydrine  thus 
obtained  with  an  alkali.  It  may  be  made  also  by  treating 
aconitic  acid  (which  see)  with  nascent  hydrogen. 

It  crystallizes  from  water  in  rhombic  prisms  which  melt  at 
157°  to  158°. 

TETR-ACID  ALCOHOLS. 

Brythrite,  C4H10O4[=CJB:6(OH)4].  —  This  substance  occurs 
in  one  of  the  algae  (Protococcus  vulgaris)  and  in  several  lichens. 
It  crystallizes  from  water  in  quadratic  prisms.  It  has  a  very 
sweet  taste.  The  fact  that  the  simplest  tetr-acid  alcohol  con- 
tains four  atoms  of  carbon  should  be  noted  specially. 


There  is  no  tetra-basic  acid  derived  from  the  hydrocarbons  of 
the  paraffin  series. 

PENT- ACID  ALCOHOLS. 

Only  one  substance  need  be  considered  under  this  head,  and 
even  this  one  is  rare.     It  is,  — 

Quercite,  C6H7(OH)5.  —  Quercite  is  formed  in  acorns.      It 
crystallizes  in  prisms  from  its  solutions  in  water. 


HEX-ACID   ALCOHOLS.  153 

No  penta-basic  acid  belonging  to  this  series  is  known. 


HEX-ACID  ALCOHOLS. 

There  are  two  isomeric  hex-acid  alcohols  known.  Both  are 
derived  from  hexane,  and  have  the  composition  represented  by 
the  formula  CCH8(OH)6.  It  will  be  noticed  that  these  hex-add 
alcohols  contain  six  carbon  atoms  each. 

Mannite,  C6H8(OH)6.  —  Mannite  is  widely  distributed  in 
the  vegetable  kingdom.  It  occurs  most  abundantly  in  manna,1 
which  is  the  partly  dried  sap  of  the  manna-ash  (Fraxinus 
ornus) .  It  is  obtained  from  incisions  in  the  bark  of  the  tree. 

Mannite  is  formed  in  the  lactic  acid  fermentation  of  sugar. 
It  is  formed  also  by  the  action  of  nascent  hydrogen  on  glucose 
and  cellulose,  or  on  inverted  cane  sugar.  This  indicates  a  close 
relationship  betiveen  the  sugars  and  mannite.  Mannite  crystal- 
lizes in  needles,  or  rhombic  prisms,  which  are  easily  soluble  in 
water  and  in  alcohol.  It  has  a  sweet  taste. 

Nitric  acid  converts  mannite  into  saccharic  acid  (which  see) . 
When  boiled  with  concentrated  hydriodic  acid,  it  is  converted 
into  secondary  hexyl  iodide,  C6H13I. 

Mannite  hexa-nitrate  (nitro-mannite),  C6H8(O.NO2)6,  is 
formed  by  treating  mannite  with  a  mixture  of  concentrated 
sulphuric  and  nitric  acids.  It  is  a  solid  substance  and  is  very 
explosive.  (Analogy  with  nitro-glycerin.) 

Mannite  hex-acetate,  C6K8(O.C2H3O)6,  is  formed  by  treat- 
ing mannite  with  acetic  anhydride.  Its  formation,  as  well  as 
that  of  the  hexa-nitrate,  shows  that  mannite  is  a  hex-acid  alcohol. 
For  the  purpose  of  making  the  acetates,  acetic  anhydride  is 
sometimes  used  instead  of  acetyl  chloride.  In  some  cases  in 

1  The  manna  of  the  Scriptures  was  obtained  from  the  branches  of  Tammarix  gallica. 
It  contained  no  mannite,  but  a  substance  of  similar  properties. 


154  DERIVATIVES    OF   THE   PARAFFINS. 

which  the  latter  will  not  work,  the  former  answers  very  well. 
Hence  acetic  anhydride  has  come  into  use  as  a  reagent,  which 
enables  us  to  decide  whether  a  substance  under  examination  is 
or  is  not  an  alcohol ;  and,  if  it  is,  to  which  class  (whether 
mon-acid,  di-acid,  tri-acid,  etc.)  it  belongs. 

Dulcite,  CGHS(OH)G. —  This  occurs  in  a  kind  of  manna 
obtained  in  Madagascar,  the  source  of  which,  however,  is 
unknown.  It  is  formed  by  treating  sugar  of  milk  or  galactose 
with  nascent  hydrogen  (compare  .with  maunite  in  this  respect) . 

Dulcite  crystallizes  in  monoclinic  prisms ;  easily  soluble  in 
water  and  in  alcohol. 

Nitric  acid  oxidizes  dulcite,  forming  mucic  acid  (which  see), 
isomeric  with  saccharic  acid,  which  is  formed  from  mannite. 
Like  mannite,  when  boiled  with  hydriodic  acid  it  yields  second- 
ary hexyl  iodide,  C6H13I.  With  acetic  anhydride  it  yields  dulcite 
hex-acetate,  C6H8(O.C2H8O)6. 


There  are  no  Jiexa-basic  acids  known  belonging  to  this  series. 

Neither  alcohols  nor  acids  are  known  containing  more  than 
six  alcoholic  or  acid  groups.  We  have,  therefore,  completed 
an  account  of  the  alcohols,  acids,  aldehydes,  ethers,  etc.,  derived 
from  the  paraffin  series  of  hydrocarbons.  But  we  are  not  yet 
prepared  to  pass  on  to  the  next  series  of  hydrocarbons.  The 
compounds  which  up  to  this  time  have  been  considered  belong 
to  distinct  classes.  Each  one,  with  very  few  exceptions,  is 
either  an  alcohol  or  an  acid,  an  aldehyde  or  a  ketone,  etc. 
The  few  exceptions  referred  to  are  the  acid  ethereal  salts,  such 

C1  TT  O 

as  ethyl-sulphuric  acid,  2  jjo  >  SO2,  which  may  be  regarded  as 
both  ethereal  salt  and  acid  at  the  same  time,  and  the  alcoholic 
ethereal  salts,  corresponding  to  basic  salts  ;  such,  for  example, 

as  glycerin  mon-acetate,  C3H5  j  .Q*   3   ,  which  may  be  regarded  as 

ethereal  salt  and  alcohol  at  the  same  time.  Such  compounds 
may  be  called  mixed  compounds. 


CHAPTER   X. 

MIXED    COMPOUNDS. -DERIVATIVES    OP 
THE    PARAFFINS. 

UNDER  this  head  are  included  such  compounds  as  belong  at 
the  same  time  to  two  or  more  of  the  chief  classes  already  con- 
sidered. Thus,  there  are  substances  which  are  at  the  same 
time  alcohols  and  acids.  There  are  others  which  are  at  the 
same  time  alcohols  and  aldehydes,  alcohols  and  ketones,  acids 
and  ketones,  etc.  Fortunately,  for  our  purpose,  the  number 
of  compounds  of  this  kind  actually  known  is  comparatively 
small,  though  among  them  are  many  of  the  most  important 
natural  compounds  of  carbon.  The  first  class  which  presents 
itself  is  that  of  the  alcohol  adds  or  add  alcohols;  that  is,  sub- 
stances which  combine  within  themselves  the  properties  of  both 
alcohol  and  acid.  They  are  commonly  called  oxy-adds  or 
hydroxy -acids. 

HYDROXY- ACIDS,  CnH2nO3. 

These  acids  may  be  regarded  either  as  monobasic  acids  into 
which  one  alcoholic  hydroxyl  has  been  introduced,  or  as  mon- 
acid  alcohols  into  which  one  carboxyl  has  been  introduced.  As 
their  acid  properties  are  more  prominent  than  the  alcoholic 
properties,  they  are  commonly  referred  to  the  acids.  Running 
parallel,  then,  to  the  series  of  fatty  acids,  we  may  look  for  a 
series  of  hydroxy-acids,  each  of  which  differs  from  the  corres- 
ponding fatty  acid  by  one  atom  of  oxygen,  or  by  containing  one 
hydroxyl  in  the  place  of  one  hydrogen,  thus  :  — 


Fatty  acids. 

Hydroxy-acids. 

H.CO2H 

HO.CO2H. 

CH3.CO2H 

CH,<OH 

CO2H 

156  DERIVATIVES    OF   THE   PARAFFINS. 


Formic  acid 
Acetic  acid 


Propionic  acid    .     .     C2H5.CO2H       C2H4- 

etc.  etc. 

The  first  member  of  the  series,  which  by  analogy  would  be 
called  hydroxy -formic  acid,  is  nothing  but  our  ordinary  hypo- 
thetical carbonic  acid.  Although  its  relation  to  formic  acid  is 
the  same  as  that  of  the  next  member  of  the  series  to  acetic 
acid,  it  certainly  has  no  properties  in  common  with  the  alcohols  ; 
but,  owing  to  its  peculiar  structure,  it  is  a  bibasic  acid  which 
the  other  members  of  the  series  are  not.  Nevertheless,  it  may 
be  referred  to  here  for  the  sake  of  a  few  of  its  derivatives, 
which  are  somewhat  allied  to  those  of  the  hydroxy-acids  proper. 

Carbonic  acid,  H2CO3f  CO  <  9^\  —  It   is   believed    that 


this  body  exists  in  solutions  of  carbon  dioxide  in  water.  All 
that  is  known  about  it  is  that  it  is  a  feeble  bibasic  acid,  and 
breaks  up  into  water  and  carbon  dioxide  whenever  it  is  set  free 
from  its  salts.  We  have  seen  that  this  instability  is  generally 
met  with  in  compounds  containing  two  hydroxyls  in  combina- 
tion with  one  carbon  atom. 

Among  the  derivatives  of  carbonic  acid  which  may  be  re- 
ferred to  at  this  time  are  the  ethereal  salts.  These  may  be 
made  :  — 

1.  By  treating  silver  carbonate,  CO  <  ^  *,  with  the  iodides 
of  alcohol  radicals  ;  as,  for  example,-— 


4-  2  C2H5I  =  CO<5  +  2  Agl. 
OAg  OC2H5 

2.    By  treating  the  alcohols  with  carbonyl  chloride,  COC12  :  — 
COC12  4-  2  C2H5OH  =  CO(OC2H5)2  4  2  HC1. 


ETHYL  CHLOR-CARBONATE.  157 

C/l 
Ethyl   chlor-carbonate,    CO  <  Z*    „.  .  —  This    compound 

UL/2.H.5 

is  made  by  treating  alcohol  with  carbonyl  chloride  :  — 

Pi 

COC12  +  C2H5OH  =  CO  <  ;*         +  HC1. 

OC2H5 

It  may  be  regarded  as  the  ethyl  salt  of  mono-chlor-formic 
acid,  Cl.COOH;  and,  properly  speaking,  should  be  called  ethyl 
cJ>  lor-  formate. 

Carbon  disulphide  acts  very  much  like  carbon  dioxide  towards 
alkalies  and  alcohols,  and  thus  a  number  of  ether  acids  and 
ethereal  salts  containing  sulphur  may  be  made.  Thus,  when 
carbon  disulphide  is  added  to  a  solution  of  caustic  potash  in 

/~\f*1    TT 

alcohol,  a  potassium  salt  of  the  formula  CS<0    2   5  is  formed. 

oK 

This  is  called  potassium  xanthogenate.  The  free  xanthogenic 
acid  is  very  unstable,  breaking  up  into  alcohol  and  carbon 
disulphide.  The  formation  of  the  salt  is  represented  by  the 
following  equation  :  — 


CS2  +  KOH  +  C2H5OH  =  CB<t  +  H2O. 

oK 

A  similar  salt  made  from  ordinary  amyl  alcohol  has  been  used 
for  the  purpose  of  destroying  phylloxera,  the  insect,  which  is  so 
destructive  to  grape-vines,  particularly  in  the  wine  districts  of 
France. 


General  methods  for  the  preparation  of  hydroxy-acids.  The 
methods  available  for  making  the  hydroxy-acids  are  modifica- 
tions of  those  used  for  making  alcohols  and  acids. 

Starting  from  a  men -acid  alcohol,  we  may  make  a  hydroxy- 
acid  b}'  the  same  methods  which  we  used  in  making  an  acid 
from  a  hydrocarbon.  Suppose,  for  example,  that  we  are  to 
make  acetic  acid  from  marsh  gas.  The  reactions  which  we 
make  use  of  are  :  (1)  the  preparation  of  a  halogen  derivative  ; 
(2)  conversion  of  the  halogen  derivative  into  the  cyanogen 


158  DERIVATIVES   OF   THE   PARAFFINS. 

derivative  ;  and  (3)  conversion  of  the  cyanogen  derivative 
into  the  acid.  We  describe  the  results  of  these  operations  by 
saying  that  we  have  introduced  carboxyl.  63*  similar  opera- 
tions we  may  introduce  carboxyl  into  methyl  alcohol,  and  the 
product  is  hydrox3T-acetic  acid. 

It  is,  however,  generally  better  to  start  from  an  acid  and  in- 
troduce hydroxyl.     This  may  be  done  in  several  ways  :  — 

1.  By  treating  a  halogen  derivative  of  an  acid  with  water  or 
silver  hydroxide  :  — 


Brom-acetic  acid. 


2.  By  treating  an  amido  derivative  of  an  acid  with  nitrous 
acid  (see  page  98)  :  — 


CH2<        2    +  HN02  =  CH2<  +  N2  +  H20. 

L^Us-tl  UL^H 

Amido-acetic  acid. 

3.  By  treating  a  sulphonic-acid   derivative  of   an  acid  with 
caustic  potash  :  — 


-  KOH  =  CH2<^       +  KHSO,. 
^u2n  CO2H 

Sulpho-acetic  acid. 

The  first  two  of  these  reactions  have  been  described  and  men- 
tioned as  affording  methods  for  the  introduction  of  hydroxyl 
into  hydrocarbons.  It  will  be  seen  that  the  only  difference 
between  the  reactions  used  in  making  alcohols  and  those  used 
in  making  hydroxy-acids  is  that  in  one  case  we  start  from  the 
hydrocarbons,  while  in  the  other  we  start  from  the  acids. 

Glycolic  acid,  hydroxy-acetic  acid,  oxy-acetic  acid, 
C2H4O3(  =  CH,  <  p^T-pr  )•  — Glycolic  acid  is  found  in  nature  in 
unripe  grapes,  and  in  the  leaves  of  the  wild  grape  (Ampelopsis 
hederacea) . 


GLYCOLIC    ACID,    ETC.  159 

It  may  be  made  from  glycocoll,  which  is  amido-acetic  acid 
(see  reaction  2,  above),  from  brom-  or  chlor-acetic  acid  and 
water  (see  reaction  1  ,  above)  ,  by  the  oxidation  of  glycol  :  — 

CH2OH  CO2H 

|  +  02  =    |  +H20. 

CH2OH  CH2OH 

Glycol.  Glycolic  acid. 

This  consists  in  transforming  one  of  the  primary  alcohol  groups, 
CH2OH,  contained  in  glycol  into  carboxyl.  (What  would  be 
formed  by  conversion  of  both  the  primary  alcohol  groups  of 
glycol  into  carboxyl  ?)  It  ma}T  also  be  made  b}~  careful  oxida- 
tion of  ethyl  alcohol  with  nitric  acid.  For  this  purpose  a 
mixture  of  alcohol  and  nitric  acid  is  allowed  to  stand  until  no 
further  action  takes  place. 

Glycolic  acid  forms  crystals  which  are  easily  soluble  in  water, 
alcohol,  and  ether. 

As  an  acid,  gly  colic  acid  forms  a  series  of  salts  with  metals, 
and  ethereal  salts  with  alcohol  radicals.  The  latter,  of  which 
ethyl  glycolate  may  be  taken  as  an  example,  may  be  made  by 
means  of  one  of  the  reactions  usually  employed  for  making 
ethereal  salts  ;  for  example,  by  treating  silver  glycolate  with 
ethl  iodide  :  — 


In  this  reaction,  as  well  as  in  the  formation  of  salts  of  gly  colic 
acid,  the  alcoholic  hydroxyl  remains  unchanged. 

As    an  alcohol,   gly  colic   acid  forms   ethers   of  which  ethyl- 
OC*  TT 

gly  colic  acid,  CH2<  m2TT3'  roay  serve  as  an  example.  It  will  be 
seen  that  this  is  isomeric  with  ethyl  glycolate.  But  while  the 
latter  has  alcoholic  properties,  the  former  has  acid  properties. 
Ethyl  glycolate  is  a  liquid  which  boils  at  160°.  Ethyl-glycolic 
acid  is  a  liquid  which  boils  at  -206°  to  207°.  Finally,  as  an 
alcohol,  gtycolic  acid  forms  ethereal  salts,  of  which  acetyl- 
gly  colic  acid  may  serve  as  an  example.  This  is  gly  colic  acid 


160  DERIVATIVES   OF   THE  PARAFFINS. 

in  which  the  hydrogen  of  the  hydroxyl  is  replaced  by  acetyl, 

o  r1  TT  o 
CH2<    '  2   3   ,  bearing,  as  will  be  seen,  the  same  relation  to 

\J\JnLJL 

gly colic  acid  and  acetic  acid  that  ethyl  acetate,  C2H5.O.C2H3O, 
bears  to  alcohol  and  acetic  acid. 

Gly  colic  acid  and  the  other  acids  of  the  same  series  lose 
water  when  heated,  and  yield  peculiar  anlvydrides.  The  product 
obtained  from  glycolic  acid  is  known  as  glycolide.  It  has 
neither  acid  nor  alcoholic  properties,  and  is,  therefore,  be- 
lieved to  be  derived  from  glycolic  acid  as  represented  in  this 
equation :  —  r. 

OTT 

CH2<™rm  =  CH2<  '      +H2°- 
CO 

Glycolide. 

Glycolide  is  insoluble  in  cold  water.  When  boiled  for  a  long 
time  with  water,  it  is  converted  into  glycolic  acid. 

Lactic  acids,  hydroxy-propionic  acids,  oxy-propionic 

acids,  C3H6O3f  =  C,H,  <  ?;?,-,.  V  —  In  speaking  of  propionic 
V  ou2±±y 

acid,  it  was  pointed  out  that  two  series  of  substitution-products  of 
the  acid  are  known,  which  are  designated  as  the  a-  and  /^-series. 
Accordingly  we  would  expect  to  find  two  hydroxy-propionic 
acids,  the  a-  and  the  /?-acid.  Two  lactic  acids  have  been 
known  for  a  long  time.  One  of  these  is  ordinary  lactic  acid; 
the  other  a  variety  which  is  found  in  flesh,  and  hence  called 
sarco-lactic  acid.  But,  strange  to  say,  a  thorough  investigation 
of  these  two  acids  has  proved  that  both  must  be  represented  by 
the  same  structural  formula,  as  both  conduct  themselves  in 
exactly  the  same  way  towards  reagents.  And,  further,  one 
other  hydroxy-propionic  acid  is  certainly  known,  and  even  a 
fourth  has  been  described.  The  facts  then  are  these :  three, 
and  probably  four,  acids  are  known,  all  of  which  are  hydroxy- 
propionic  acids.  Our  theory  enables  us  to  foretell  the  existence 
of  only  two.  Before  discussing  this  discrepancy  let  us  briefly 
consider  the  acids  themselves. 


LACTIC   ACIDS.  161 

1.  Lactic  acid,  inactive   ethylidene-lactic  acid,  a-hy- 

OH 
droxy-propionic  acid,  CH3.CH  <         H.  —  The  chief  method 


for  making  lactic  acid  consists  in  the  fermentation  of  sugar 
by  the  lactic-acid  ferment.  This  process  has  already  been 
described  under  the  head  of  Butyric  Acid.  It  is  carried  out 
best  by  dissolving  cane  sugar  and  a  little  tartaric  acid  in 
water;  then  adding  putrid  cheese,  milk,  and  zinc  carbonate. 
The  object  of  the  zinc  carbonate  is  to  prevent  the  solution 
from  becoming  acid,  as  the  presence  of  free  acid  is  fatal  to  the 
ferment.  The  sugar  is  converted  first  into  glucose,  C6H12O6  ; 
and  this  then  breaks  up  into  lactic  acid  :  — 

C6H12O6  =  2  C3H6O3. 

It  will  be  remembered  that  by  continued  action  of  the  ferment 
on  the  lactic  acid,  butyric  acid  is  formed  (see  Butyric  Acid). 
Lactic  acid  may  be  made  also  by  fermentation  of  sugar  of 
milk,  and  is  hence  contained  in  sour  milk  ;  by  boiling  a-chlor- 
propionic  acid  with  alkalies,  — 

CH3.CH<C1     T  +  KOH  =  CH3.CH<°^TT  +  KC1; 

Gv^Il  vyL^Ai 

and  by  treating  alanine  (a-amido-propionic  acid)  with  nitrous 
acid,  — 

CH3  .CH  <        2    +  HN02  =  CH3  .CH  <  +  N2  +  H2O. 


Lactic  acid  is  a  thick  liquid  which  mixes  with  water  and 
with  alcohol  in  all  proportions. 

Treated  with  hydriodic  acid,  it  is  reduced  to  propionic  acid. 
Treated  with  hydrobromic  acid,  it  yields  a-brom-propionic  acid. 

2.    Sarco-lactic    acid,    active    ethylidene-lactic   acid, 

OTT 

CH3.CH  <  X^TT-  —  This  acid  occurs  in  the  liquids  expressed 
CO2H 

from  meat.      It  is  therefore  contained  in  "extract  of  meat," 
and  may  be  obtained  most  readily  from  this  source. 


162  DERIVATIVES    OF   THE   PARAFFINS. 

Its  properties  are,  for  the  most  part,  like  those  of  inactive 
lactic  acid,  and  its  conduct  towards  reagents  is  in  all  respects 
the  same.  Its  salts  are  somewhat  more  easily  soluble  than 
those  of  ordinary  inactive  lactic  acid.  The  chief  difference 
between  the  two  is  observed  in  the  action  towards  polarized 
light.  Active  lactic  acid  turns  the  plane  of  polarization  to  the 
right.  It  is  dextro-rotatory.  Its  salts  are  all  laevo-rotatory. 
On  the  other  hand,  neither  inactive  lactic  acid  nor  its  salts 
exert  any  action  upon  polarized  light.1 

3.  Hydracrylic  acid,  j  CH2OH 

P-Hydroxy-propionic  acid,  J  CH,  .CO2H* 
Hydracrylic  acid  is  made  by  boiling  /8-iodo-propionic  acid  with 
water  or  silver  oxide  and  water  :  — 

CH2I  CHo.OH 

|  +  HHO  =  |  +  HI. 

CH2.CO2H  CH2.CO2H 

CH2 

It  is  made  also  by  starting  with  ethylene,    I      .     When  this 

CH2 

hydrocarbon  is  treated  with  hypochlorous  acid,  HOC1,  it  is  con- 

CH2C1 

verted  into  ethvlene-chlorhydrine,    |  (which  see),  which 

CH2OH 

may  be  made  by  treating  ethylene   alcohol  with  hydrochloric 

acid :  — 

CH2OH  CH2C1 

|  +  HC1  =  |  4-  H2O. 

CH2OH  CH2OH 

By  replacing  the  chlorine  with  cyanogen,  and  boiling  the  cyan- 

CH2OH 
hydrine,  I  ,  thus  obtained,  with  an  alkali,  hydracrylic  acid 

CH2CN 
is  obtained. 

These  reactions  clearly  show  that  hydracrylic  acid  is  an 
ethylene  compound,  and,  as  it  is  made  from  /5-iodo-propionic 

1  See  active  and  inactive  amyl  alcohols,  p.  126. 


ETHYLENE-LACTiC   ACID.  163 

acid  by  replacing  the  iodine  with  hydroxyl,  it  follows  further 
that  the  /3-substitution-products  of  propionic  acid  are  ethylene 
products,  and  that  the  a-products  are  ethylidene  products  (see 
p.  131). 

Hydracrylic  acid  is  a  syrup.  Its  salts  differ  markedly  from 
those  of  the  inactive  and  active  lactic  acids.  When  heated,  it 
loses  water  and  is  transformed  into  acrylic  acid,  CH2.CH.CO2H 
(which  see). 

The  difference  in  conduct  between  ethylidene-lactic  acid  and 
ethylene-lactic  acid,  when  heated,  is  interesting  and  suggestive. 
When  ethylidene-lactic  acid  is  heated,  both  its  acid  and  alco- 
holic properties  are  destroyed,  both  the  alcoholic  and  acid 
hydroxyls  taking  part  in  the  reaction.  Whereas,  when  ethyl- 
ene-lactic acid  is  heated,  only  the  alcoholic  properties  are 
destroyed,  the  carboxyl  remaining  intact. 

4.  Ethylene-lactic  acid.  —  A  fourth  hydroxy-propionic 
acid,  called  ethylene-lactic  acid,  has  been  described  as  occur- 
ring in  meat.  There  appears,  however,  to  be  some  little  doubt 
in  regard  to  its  existence. 

Without  reference  to  the  fourth  doubtful  lactic  acid,  the  fact 
remains  that  there  are  more  hydroxy-propionic  acids  known 
than  our  theory  can  account  for.  Other  cases  of  this  kind  are 
known,  and  one  very  marked  and  especially  interesting  one 
will  be  referred  to  when  tartaric  acid  is  considered.  It  will  be 
shown  that  just  as  there  is  an  active  and  an  inactive  lactic  acid, 
so  there  is  an  active  and  an  inactive  tartaric  acid,  which  con- 
duct themselves  in  the  same  way  towards  reagents,  and  must 
hence  be  represented  by  the  same  structural  formula. 

Apparently  we  have  here  to  deal  with  a  new  kind  of  isome- 
rism.  Bodies  may  conduct  themselves  chemically  in  exactly 
the  same  way,  and  yet  differ  in  some  of  their  physical  proper- 
ties, as  in  their  action  towards  polarized  light.  To  distinguish 
this  kind  of  isomerism  from  ordinary  chemical  isomerism  it  is 
called  physical  isomerism. 


164 


DERIVATIVES   OF   THE  PARAFFINS. 


An  ingenious  hypothesis  has  been  put  forward  by  way  of 
explanation  of  that  particular  kind  of  physical  isomerism  which 
shows  itself  in  the  action  of  compounds  upon  polarized  light. 
It  must  be  remembered  that  our  ordinary  formulas  have  nothing 
whatever  to  do  with  the  relations  of  the  atoms  and  groups  in 
space.  The}'  indicate  chemical  relations  which  are  discovered 
by  a  study  of  chemical  reactions.  At  present,  it  is  hazardous 
to  indulge  in  speculations  regarding  the  relations  of  the  parts 
in  space,  and,  while  the  hypothesis  which  is  to  be  explained 
briefly  is  ingenious  and  interesting,  the  student  should  be  careful 
not  to  be  carried  away  by  it.  He  should  remember  that  it  is 
only  a  thought. 

Let  us  suppose  that  in  a  carbon  compound  one  carbon  atom 
is  situated  at  the  centre  of  a  tetrahedron,  and  that  the  four 
atoms  or  groups  which  it  holds  in  combination  are  at  the  angles 
of  the  tetrahedron  as  represented  in  Fig.  10. 

If  these  groups  are  all  different  in  kind,  and  only  in  this 
case,  it  is  possible  to  arrange  them  in  two  ways  with  reference 
to  the  carbon  atom.  The  difference  between  the  two  arrange- 


ments is  that  which  is  observed  between  either  one  and  its 
reflection  in  a  mirror.  Imperfectly  the  second  arrangement  of 
the  figure  above  represented  is  shown  in  Fig.  1 1 . 

A  carbon  atom,  in  combination  with  four  different  kinds  of 
atoms  or  groups,  is  called  an  asymmetrical  carbon  atom. 
Whenever,  therefore,  a  compound  contains  an  asymmetrical 


HYDROXY-ACIDS,    CuH2nO4.  165 

carbon  atom,  there  are  two  possible  arrangements  of  its  parts 
in  space  which  correspond  to  the  two  complementary  tetra- 
hedrons, viz.,  the  right-handed  and  the  left-handed  tetrahedron. 
In  ethylidene  lactic  acid  there  is  an  asymmetrical  carbon  atom, 
as  shown  by  the  ordinary  formula,  which  may  be  written  thus  : 

H 
I 
CH3  -  C  —  OH,  the  central  carbon  atom  appearing  in  combination 

C02H 

with  (1)  hydrogen,  (2)  hydroxyl,  (3)  carboxyl,  and  (4)  methyl. 
Hence,  according  to  the  hypothesis  just  stated,  there  ought  to 
be  two  possible  arrangements  of  the  parts  of  a  compound 
containing  this  group,  one  corresponding  to  the  right-handed 
tetrahedron,  the  other  to  the  left-handed  tetrahedron.  Both 
would  be  ethylidene-lactic  acids.  Thus  we  have  at  least  a 
plausible  explanation  of  the  existence  of  two  ethylidene-lactic 
acids. 

NOTE  FOR   STUDENT.  —  Has  active  amyl  alcohol  an  asymmetrical 
carbon  atom  ? 

There  are  several  Irydroxy-butyric  and  valeric  acids  known, 
but  they  need  not  be  considered  here. 


HYDROXY- ACIDS,  CnH2nO4. 

The  acids  just  considered  may  be  called  monohydroxy-mono- 
basic  acids.  Similarly,  there  are  dihydroxy -monobasic  acids, 
which  may  be  regarded  as  derived  from  the  monohydroxy-acids 
by  the  introduction  of  a  second  hydroxyl.  Thus,  if  into  lactic 

C*()  TT 

acid,   CH3.CH<_TT2    ,   a  second   hvdroxvl  be  introduced,   the 

OH 

CH2.OH 

product  would   have  the  formula    CH.OH-      This  is  the  best 


known  dihydroxy -monobasic  acid  of  the  paraffin  series. 


166  DERIVATIVES   OF   THE  PARAFFINS. 

/     CH2OHx 
Glyceric  acid,  QAOJ  =  CHOH    .  —  This  acid  has  been 

V     CO2H    / 

referred  to  as  the  first  product  of  the  oxidation  of  glycerin.  It 
is  prepared  by  allowing  glycerin  and  nitric  acid  to  stand  together 
at  the  ordinary  temperature  for  some  time,  and  then  heating  on 
the  water-bath.  It  may  be  made  also  by  treating  one  of  the 
chlor-lactic  acids  with  water. 

NOTE  FOR  STUDENT.  —  Explain  this  reaction. 

Glyceric  acid  is  a  thick  syrup  which  mixes  with  water  and 
alcohol.  When  treated  with  very  concentrated  hydriodic  acid, 
it  is  converted  into  /2-iodo-propionic  acid.  This  conversion 
involves  two  reactions  :  — 


(1) 


CH9OH 

CH2I 

1 

1 

CHOH  + 

HI  =  CHOH  -f  H2O,  and 

1 

1 

C02H 

CO2H 

CH2I 

CH2I 

1 

1 

CHOH  + 

2  HI  =  CH2       +  H2O  +  2  I 

1 

1 

C02H 

C02H 

(2) 


HYDROXY-ACIDS,  CnH2n_2O<5. 

The  acids  included  under  this  head  are  monohydroxy-dibasic 
adds.  They  bear  the  same  relation  to  the  dibasic  acids  of  the 
oxalic  acid  series  that  the  simplest  hydroxy-acids  bear  to  the 
members  of  the  formic  acid  series.  The  principal  members  of 
this  series,  and  the  only  ones  which  will  be  considered,  are 
tartronic  acid  and  malic  acid. 


MALIC   ACID.  167 


Tartronic  acid,  C3HA>  -CH(OH)<  ~~2£  *  ~  This  acid 

V  OU2±i/ 

is  prepared  by  an  indirect  method  from  tartaric  acid.     It  may 

l)e  made,  — 

(1)    By   boiling   brom-malonic   acid   with   silver   oxide  and 
water  :  — 

CHBr  <  +  AgQH  =  CH(OH)  <  +  AgBr  ; 


(2)  By  treating  brom-cyan-acetic  acid  with  caustic  potash  :  — 

CHBr  <  ™  T  +  2  KOH  +  H2O 
C(J2H 

=  CH(OH)  <C°*K  +  NH3  +  KBr. 
l^U2ti 

Tartronic  acid  is  a  solid  which  crystallizes  in  prismatic  crystals. 
It  is  easily  soluble  in  water,  alcohol,  and  ether.  It  melts  at 
182°.  At  155°  it  gives  off  carbon  dioxide  and  water,  and  is 
converted  into  glycolide  (which  see)  :  —  ' 

(1)  CH(OH)<CO£  =  CH2<OHH  +  C02 

Glycolic  acid. 

o 

(2)  CH*<™   T  =  CH2<   I     +  H20. 


C02H 


CO 

Glycolide. 


NOTE  FOR  STUDENT.  —  Compare  reaction  (1)  with  that  which  takes 
place  when  iso-succinic  acid  is  heated,  and  note  the  analogy. 

Hydroxy-succinic  acids,  C4H6O5f=C2H3(OH)<S52SV  — 

\  OU2xl  / 

Three  hydroxy-succmic  acids  have  been  described,  the  principal 

one  being  ordinary  malic  acid. 

/    CH(OH).CO,H\ 
Malic  acid,  C4HGO5  =  I  .  —  This  acid  is  very 

V    CH2.CCXH 
widely  distributed  in  the  vegetable  kingdom,  as  in  the  berries 

of  the  mountain  ash,  in  apples,  cherries,  etc. 
It  is  best  prepared  from  the  berries  of  the  mountain  ash 


168  DERIVATIVES   OF  THE  PARAFFINS. 

which  have  not  quite  reached  ripeness.  The  berries  are  pressed 
and  boiled  with  milk  of  lime.  The  acid  passes  into  solution  as 
the  calcium  salt,  and  this  is  purified  by  crystallization. 

It  may  be  made  also  b}~  treating  aspartic  acid,  which  is  amiclo- 

C^C\  TT 

succinic  acid,  C2H3(NH2)  <      *„,  with  nitrous  acid,  and  by  treat- 

vy  V/o-tl 

ing  tartaric  acid  with  hydriodic  acid.  This  latter  reaction  will 
be  explained  when  tartaric  acid  is  considered.  Tartaric  and 
malic  acids  are  closely  related  to  each  other,  and  both  are 
related  to  succinic  acid,  as  will  appear  from  the  reactions. 

Malic  acid  is  a  solid  substance  which  crystallizes  with  diffi- 
cult}T.  It  is  very  easily  soluble  in  water  and  in  alcohol.  Its 
solutions  turn  the  plane  of  polarization  to  the  right  or  to  the  left, 
according  to  the  concentration. 

When  heated  it  loses  water  and  yields  either  fumaric  or 
maleic  acid  (which  see)  ,  according  to  the  temperature.  These 
acids  are  isomeric,  and  both  are  represented  by  the  formula 

f*.f\    TT 

C2H2<      *„•      The  reaction  mentioned  is  represented  by  the 

UO2li 

following  equation  :  — 


xr  it        -^  Fumaric  or 

Malic  acid.  maleic  acid. 

NOTE  FOR  STUDENT.  —  Compare  this  reaction  with  that  which  takes 
place  when  hydracrylic  acid  is  heated,  and  note  the  analogy. 

When  treated  with  hydriodic  acid,  malic  acid  is  reduced  to 
succinic  acid. 

NOTE  FOR  STUDENT.  —  Compare  this  reaction  with  the  conduct  of 
lactic  and  glyceric  acids  when  treated  with  hydriodic  acid. 

Treated  with  hydrobromic  acid,  malic  acid  is  converted  into 
mono-brom-succinic  acid. 

The  reactions  just  described  show  clearly  that  malic  acid  is 
hydroxy-succinic  acid.  Nevertheless,  if  hydroxy-succiuic  acid 
be  made  by  treating  brom-succinic  acid  with  silver  oxide  and 


INACTIVE  MALIC   ACID.  169 

water,  the  product  is  not  identical  with  ordinary  malic  acid, 
though  the  two  resemble  each  other  very  closely.  The  acid 
thus  obtained  is  — 

(~*(~\  TT 

Inactive  malic  acid,  C,H-(OH)  <  ~X25-  —  Inactive  malic 

L»vJ2xi 

acid  may  be  made  not  only  by  the  method  first  mentioned,  but 
by  several  others,  which  indicate  that  the  relation  between  it 
and  succinic  acid  is  that  expressed  in  the  formula  given.  It, 
like  ordinary  malic  acid,  is  unquestionably  a  hydroxy-succinic 
acid,  and  both  are  derived  from  ordinary  succinic  acid. 

Other  reactions  for  the  preparation  of   inactive  malic  acid 
are,  — 

( 1 )  By  treating  dichlor-propionic  acid  with  potassium  cyanide , 
and  boiling  the  product  with  caustic  potash  :  — 

CH2C1.CHC1.C02H  +  KCN 

CH2CN 

=    1  +  KC1 ; 

CHC1.CO2H 

CH2CN 

and          |  +  2  KOH  +  H2O 

CHC1.C02H 

CH2.CO2K 

=    |  +  KC1  +  NH3. 

CH(OH).CO2H 

(2)  By  heating  fumaric  acid  with  water  :  — 
CA<CoJ  +  H20  =  C2H3(OH)<CO*H;  an(J 

(3)  By  reduction  of  racemic  acid  with  hydriodic  acid.     Ra- 
ce mic  acid  has  the  same  composition  as  tartaric  acid.      The 
latter,   when  treated  with  hydriodic  acid,  yields   active  malic 
acid. 

The   properties  of   inactive  malic  acid  are  very  much  like 
those  of  active  malic  acid.     As  regards  their  chemical  conduct 


170  DERIVATIVES   OF  THE  PARAFFINS. 

they  are  almost  identical.  The  principal  difference  between 
them  is  observed  in  their  conduct  towards  polarized  light. 
They  present  a  new  case  of  physical  isomerism  of  the  same 
kind  as  that  referred  to  in  connection  with  the  lactic  acids 
(which  see).  The  same  hypothesis  may  be  applied  to  this 
case,  for  malic  acid  contains  an  asymmetrical  carbon  atom,  as 
will  be  seen  by  writing  the  formula  in  this  way  :  — 

H 

I 

CO2H-C-OH. 
I 
CH2.CO2H 

HYDROXY-  ACIDS  ,  CnH2  n  _  2  O6  . 

These  are  di-hydroxy  '-dibasic  acids.  The  chief  members  of 
the  group  are  mesoxalic  acid  and  the  different  modifications 
of  tartaric  acid. 


Mesoxalic  acid,  C3H4O=  C(OH),  <       2        —  This  acid 

y  L>(J,r±J 

is  obtained  by  indirect  and  rather  complicated  reactions  from 
uric  acid  (which  see).  It  has  been  made  also  by  boiling  di- 
brom-malonic  acid  with  baryta-water. 

NOTE  FOR  STUDENT.  —  Explain  this  reaction. 

The  acid  forms  deliquescent  needles.  When  boiled  it  loses 
carbon  dioxide  and  water,  and  glyoxylic  acid,  which  is  an  alde- 
hyde and  acid  related  to  oxalic  acid,  is  formed  :  — 

rn  TT        CHO 

C(OH)2<^25  =1         +  C02  -f  H20. 
CU2l±       C02H 

Glyoxylic  acid. 

This  acid  affords  an  example  of  a  very  rare  condition;  viz., 
the  existence  of  a  compound  in  which  two  hydroxyls  are  in 
combination  with  one  and  the  same  carbon  atom. 


TARTARIC   ACID.  171 


/  f^O  TT\ 

Di-hydroxy-succinic  acids,  OAO«I=  C2H2(OH)2<^Q2H  J 

CH(OH).C02H 

1.  Tartaric    acid,     I  .  —  Ordinary  tartaric  acid 

CH(OH).CO,H 

occurs  very  widely  distributed  in  fruits,  sometimes  free,  some- 
times in  the  form  of  the  potassium  or  calcium  salt  ;  as,  for 
example,  in  grapes,  berries  of  the  mountain  ash,  potatoes, 
cucumbers,  etc.,  etc. 

It  may  be  made  by  the  following  methods  :  — 

(1)  By  oxidizing  sugar  of  milk  with  nitric  acid; 

(2)  Also  by  oxidizing  cane  sugar,  starch,  glucose,  and  other 
similar  substances.  , 

Tartaric  acid  is  prepared  from  "tartar,"  which  is  impure 
acid  potassium  tartrate.  When  grape  juice  ferments  this  salt 
is  deposited.  It  is  purified  by  crystallization,  converted  into 
the  calcium  salt  by  treating  it  with  chalk,  and  the  calcium  salt 
then  decomposed  by  means  of  sulphuric  acid. 

The  acid  crystallizes  in  large  rnonoclinic  prisms,  which  are 
easily  soluble  in  water  and  alcohol.  It  melts  at  135°.  Its 
solution  turns  the  plane  of  polarization  to  the  right. 

Treated  with  hydriodic  acid,  tartaric  acid  yields  first  malic 
acid  and  then  ordinary  succinic  acid  :  — 


(1) 


(2)       C2H3(OH) 


=  C2H3(OH)<       •     +  H20  +  I2  ; 

HJ«>ri 

Malic  acid. 


Succinic  acid. 


While  malic  acid  is   mono-hydroxy-succinic    acid,   ordinary 
tartaric  acid  appears  to  be  di-hydroxy-succinic  acid.     But,  just 


172  DERIVATIVES    OF   THE   PARAFFINS. 

as  we  found  that  the  malic  acid  prepared  from  mono-brom-suo 
cinic  acid  is  optically  inactive,  and  therefore  different  from 
natural,  active  malic  acid,  so  too  it  has  been  found  that  the 
tartaric  acid  prepared  from  di-brom-succinic  acid  is  optically 
inactive,  and  therefore  different  from  ordinary  tartaric  acid. 
The  relations  between  the  natural  and  the  artificial  acids  will 
be  considered  more  fully  below. 

Tartrates.  Among  the  salts  the  following  may  be  mentioned 
specially  :  — 

Mono-potassium  tartrate,  KH.C4H4O6.  This  is  the  chief 
constituent  of  tartar.  In  pure  form,  as  used  in  medicine,  it  is 
known  under  the  name  of  cream  of  tartar. 

/Sodium-potassium  tartrate,  KNa.C4H4O6  +  4  H2O.  This 
salt  crystallizes  very  beautifully.  It  is  known  as  Rochelle  salt 
or  Seignette  salt. 

Calcium  tartrate,  Ca.C4H4O6  +  4  H2O.  This  salt  occurs  in 
senna  leaves  and  in  grapes.  It  forms  a  crystalline  powder  or 
rhombic  octahedrons. 

Potassium  -  antimonyl  tartrate,  K  (  SbO  )  .  C4H4O6  +  \  H2O  . 
This  is  known  as  tartar  emetic.  It  is  prepared  by  digesting 
antimonic  oxide  with  mono-potassium  tartrate.  It  crystallizes 
in  rhombic  octahedrons.  It  loses  its  water  of  crystallization  at 
100°,  and  at  200  to  220°  is  converted  into  an  antimony  potas- 
sium salt  of  the  formula  KSb.C4H2O6. 


2.  Racemic  acid,  GtHeOo  +  ELO.  —  Racemic  acid  occurs, 
together  with  tartaric  acid,  in  many  kinds  of  grapes,  and,  on 
recrystallizing  the  crude  tartar,  acid  potassium  racemate,  being 
more  soluble  than  the  tartrate,  remains  in  the  mother  liquors. 
Racemic  acid  is  formed  by  boiling  ordinary  tartaric  acid  with 
water,  or  with  hydrochloric  acid.  If  tartaric  acid  be  heated 
with  water  in  sealed  tubes  at  175°,  it  is  almost  completely 
transformed  into  racemic  acid.  It  is  formed  further  by  oxida- 
tion of  dulcite,  mannite,  cane  sugar,  gum,  etc.,  with  nitric 
acid.  It,  together  with  a  third  variety  of  tartaric  acid,  known  as 


RACEMIC    ACID.  178 

inactive  tartaric  acid,  is  formed  when  bibrom-succinic  acid  is 
treated  ivith  silver  oxide  and  water. 

Racemic  acid  differs  from  tartaric  acid  in  many  ways.  It 
crystallizes  differently,  and  contains  water  of  crystallization. 
It  is  less  soluble  than  tartaric  acid.  It  produces  precipitates 
in  solutions  of  lime  salts,  while  tartaric  acid  does  not.  Racemic 
acid  is  optically  inactive,  while  tartaric  acid  is  dextro-rotatory. 
On  the  other  hand,  racemic  and  tartaric  acids  conduct  them- 
selves towards  most  reagents  exactly  alike. 

Thus  far  the  relations  between  racemic  and  tartaric  acids 
appear  very  much  like  those  which  are  observed  between  active 
and  inactive  lactic  acids  and  between  active  and  inactive  malic 
acids.  But  there  remains  to  be  described  an  extremely  inter- 
esting experiment,  which  throws  new  light  upon  the  relations 
between  tartaric  and  racemic  acids. 

When  a  solution  of  ammonium-sodium  racemate, 

(NH4)Na.C4H406, 

is  allowed  to  evaporate  spontaneously,  beautiful  large  crystals 
are  deposited.  On  examining  these  carefully,  they  are  found 
to  be  of  two  kinds.  On  the  crystals  of  one  kind  certain  hemi- 
hedral  faces  are  developed,  while  on  the  crystals  of  the  other 
kind  the  complementary  hemihedral  faces  are  developed ;  so 
that  if  a  crystal  of  one  kind  is  placed  in  front  of  a  mirror, 
its  reflection  will  represent  the  arrangement  of  the  hemihedral 
faces  met  with  on  a  crystal  of  the  other  kind.  The  crystals 
may  be  separated  into  right-handed,  or  those  which  have  the 
right-handed  hemihedral  faces,  and  left-handed,  or  those  which 
have  the  left-handed  hemihedral  faces. 

On  separating  the  acid  from  the  right-handed  crystals  it  is 
found  to  be  ordinary  dextro-rotatory  tartaric  acid;  while  the 
acid  from  the  left-handed  crystals  is  an  isomeric  substance 
called  Icevo-rotatory  tartaric  acid.  When  these  two  varieties 
of  tartaric  acid  are  brought  together  in  solution,  they  unite,  the 
action  being  attended  by  an  elevation  of  temperature,  and  the 
result  is  racemic  acid. 


174  DEBIVATIVES   OF    THE   PARAFFINS. 

We  see  thus  that  the  inactive  racemic  acid  consists  of  two 
optically  active  substances  in  combination,  one  of  which,  ordinary 
tartaric  acid,  is  dextro-rotatory,  and  the  other  laevo-rotatory. 

Inactive  malic  acid  has  been  resolved  into  two  active  vari 
eties,   one   of    which  is   dextro-rotatory  and   the   other  laevo- 
rotatory.     And  it  is  not  improbable  that  inactive  lactic  acid 
may  be  resolved  in  a  similar  way. 

Inactive  tartaric  acid  is  very  similar  to  racemic  acid.  It 
is  formed  together  with  racemic  acid  by  treating  dibrom-suc- 
cinic  acid  with  silver  oxide  and  water.  Nothing  is  known 
regarding  the  relation  of  this  substance  to  the  other  tartaric 
acids. 

HYDROXY-  ACIDS,  CnH2n_4O7. 

These  are  mono-hydroxy-tribasic  acids.  Citric  acid  is  the 
only  one  known. 


Citric  acid,   C6H8O7  +  H2O  -  C3H4(OH)    CO2H  ).  —  Citric 


acid,  like  malic  and  tartaric  acids,  is  very  widely  distributed  in 
nature  in  many  varieties  of  fruit,  especially  in  lemons,  in  which 
it  occurs  in  the  free  condition.  It  is  found  in  currants,  whortle- 
berries, raspberries,  gooseberries,  etc.,  etc. 

It  is  prepared  from  lemon  juice.  This  is  allowed  to  ferment 
and  is  then  treated  with  lime.  The  lime  salt  is  thus  obtained 
in  the  form  of  a  precipitate,  is  collected,  and  decomposed  with 
sulphuric  acid.  100  parts  of  lemons  yield  5J  parts  of  the  acid. 

Citric  acid  crystallizes  in  rhombic  prisms  which  are  very  easily 
soluble  in  water.  The  crystallized  acid  melts  at  100°,  the 
anhydrous  at  153°  to  154°.  Heated  to  175°  it  loses  water  and 
yields  aconitic  acid  (which  see)  :  — 

c  CO2H  r  CO2H 

C3H4(OH)  1  CO2H  =  C3H3]  CO2H  +  H2O. 
lC02H  tCO2H 

Aconitic  acid. 


CITRIC    ACID.  175 

NOTE  FOR  STUDENT.  —  Compare  with  formation  of  acrylic  from 
hydracrylic  acid;  and  of  rnaleic  and  fumaric  acids  from  malic  acid. 

Aconitic  acid  takes  up  hydrogen,  and  is  transformed  into  tri- 
carballylic  acid  (which  see) .  Thus  a  clear  connection  between 
tricarballylic  acid  and  citric  acid  is  traced,  the  latter  appearing 
as  hydroxy-tricarballylic  acid.  Citric  acid  has  been  made  arti- 
ficially by  a  somewhat  complicated  method. 

When  subjected  to  dry  distillation,  citric  acid  loses  both  water 

and  carbon  dioxide,   and  yields  citraconic  acid,  C3H4  <  ^°2H^ 

CO2H 

(which  see)  ;  if  heated  with  water  or  dilute  sulphuric  acid  to 
160°  it  yields  itaconic  acid,  C3H4<^2H,  (which  see). 

(  CO2H 

C3H4(OH)  ]  CO2H  =  C3H4  j  C°2H  +  H2O  +  CO2. 
IC02H  '°2H 

Citraconic  or  ita- 
conic acid. 

NOTE  FOR   STUDENT.  —  What  relation,  as  far  as   composition  is 

t  r*c\  TT 
concerned,  do  these  two  acids  of  the  formula  C3H4  j  ppvVr  bear  to 

fumaric  and  malei'c  acids?    By  distillation  of  what  acid  are  the  two 
latter  formed? 

Citrates.     A  few  of  the  salts  of  citric  acid  are  mentioned  :  — 

Mono-potassium  citrate,  KH2.C6H5O7  +  2  H2O  ; 

Di-potassium  citrate,  K2H  .C6H5O7 ; 

Tri-potassium  citrate,  K3.C6H5O7  -f-  H2O.  All  these  potas- 
sium salts  are  easily  soluble  in  water.  They  are  made  by 
mixing  citric  acid  and  potassium  carbonate  in  the  right  pro- 
portions. 

Calcium  citrate,  Ca3(C6H5O7)2  -f-  4  H2O.  This  salt  is  formed 
by  mixing  a  citrate  of  an  alkali  with  calcium  chloride.  It  is 
more  easily  soluble  in  cold  than  in  hot  water ;  hence  boiling 
causes  a  precipitate  in  dilute  solutions. 

Magnesium  citrate,  Mg3(C6H5O7)2  -f-  14H2O.  This  may  be 
made  by  dissolving  magnesia  in  citric  acid.  It  is  used  in 
medicine. 


176  DERIVATIVES    OF   THE   PARAFFINS. 

V 

HYDROXY-ACIDS,  CnH2n_2O8. 

There  are  two  acids  to  be  considered  under  this  head.     They 
are  isomeric,  and  both  are  tetra-hydroxy-dibasic. 


=  C4H4(OH)4<  ~X2TT  •  —  Saccharic 
ou2±iy 

acid  is  formed  by  the  oxidation  of  cane  sugar,  glucose,  or  sugar 
of  milk  with  nitric  acid. 

To  prepare  it,  it  is  best  to  treat  ordinary  sugar  with  dilute 
nitric  acid.  Oxalic  acid  is  formed  at  the  same  time. 

It  is  an  amorphous  mass,  which  becomes  solid  only  with 
difficulty.  When  treated  with  hydriodic  acid  it  is  converted 
into  adipic  acid,  a  member  of  the  oxalic  acid  series  (see  table, 
page  142)  :  - 

C4H4(OH)4  <  Jgg  +  8  HI  =  C4H8  <  jgg  +  4  H20  +  8  I. 

Saccharic  acid.  Adipic  acid. 

NOTE  FOR  STUDENT.  —  What  relations  exist  between  hexane,  man- 
nite,  adipic  acid,  and  saccharic  acid? 

Mucic  acid,  C6H10O8(  -  C4H4(OH)4  <  29®-  —  Mucic  acid 
\  UVJ^Jtly 

is  formed  by  oxidizing  sugar  of  milk,  the  gums,  or  dulcite,  with 
nitric  acid. 

It  is  best  prepared  by  boiling  sugar  of  milk  with  ordinary 
nitric  acid.  Oxalic  and  tartaric  acids  are  formed  at  the  same 
time. 

It  is  a  crystalline  powder  which  is  very  difficultly  soluble  in 
cold  water.  Hydriodic  acid  converts  it  into  adipic  acid  (see 
above,  under  Saccharic  Acid). 


CHAPTER   XI. 
CARBOHYDRATES. 

AMONG  the  mixed  compounds,  or  compounds  which  belong  at 
the  same  time  to  more  than  one  of  the  fundamental  classes  of 
carbon  compounds,  are  the  important  bodies  called  carbohy- 
drates. This  name  was  originally  given  to  them  because  the 
hydrogen  and  oxygen  which  enter  into  their  composition  are 
always  present  in  the  proportion  to  form  water,  as  shown  in  the 
formulas  for  dextrose,  C6H12O6,  starch,  C6H10O5,  etc.  All  the 
compounds  belonging  to  the  class  of  carbohydrates  are  more  or 
less  intimatel}'  related  to  the  hex-acid  alcohols,  mannite  and 
dulcite,  C6H8(OH)6.  According  to  their  composition,  they  fall 
naturally  into  three  groups.  These  are  :  — 

1.  The  glucose  group  of  the  formula  C6H12O6. 

The  principal  members  of  this  group  are  dextrose  or  grape 
sugar,  levulose  or  fruit  sugar,  and  galactose. 

2.  The  cane  sugar  group  of  the  formula  C12H22On. 

The  principal  members  are  cane  sugar,  sugar  of  milk,  and 
maltose. 

3.  The  cellulose  group  of  the  formula  (C6H10O5)X. 

The  principal  members  are  cellulose,  starch,  gum,  and  dextrin. 

THE  GLUCOSE  GROUP,  C6H12O6. 

Dextrose,  glucose,  grape  sugar,  C6H12O6.  —  Dextrose 
occurs  very  widely  distributed  in  the  vegetable  kingdom,  par- 
ticularly in  sweet  fruits,  in  which  it  is  found  together  with  an 
equivalent  quantity  of  levulose.  It  is  found  in  honey  together 
with  cane  sugar  and  some  levulose.  It  occurs,  further,  in  the 
blood,  in  the  liver,  and  in  the  urine ;  and,  in  the  disease  called 


178  CARBOHYDRATES. 

Diabetes  melHtus,  the  quantity  contained  in  the  urine  is  largely 
increased,  reaching  as  much  as  8  to  10  per  cent. 

Dextrose  is  formed  from  several  of  the  carbohydrates  of  the 
formulas  C^H^On  and  C6H10O5,  'by  boiling  with  dilute  mineral 
acids,  or  by  the  action  of  ferments.  The  formation  from  cane 
sugar  takes  place  according  to  this  equation,  equivalent  quanti- 
ties of  dextrose  and  levulose  being  formed  :  — 

C12H22On  +  H20  =  C6H1206  +  C6H1206. 

Cane  sugar.  Dextrose.  Levulose. 

Starch,  cellulose,  and  dextrin  yield  dextrose  according  to  this 
equation :  — 

CgH10O5  -f~  H2O  =  C6H12O6. 

Finally,  dextrose  occurs  in  nature,  in  combination  with  a 
number  of  carbon  compounds,  in  the  so-called  glucosides.  These 
break  up  easily  when  treated  with  dilute  mineral  acids  or  fer- 
ments, and  3'ield  dextrose  as  one  of  the  products  (see  Glucos- 
ides). Examples  of  the  glucosides  are  amygdalin,  agsculin, 
quercitrin,  etc. 

Dextrose  is  prepared  on  the  large  scale  from  corn  starch  in 
the  United  States,  and  from  potato  starch  in  Germany.  The 
transformation  is  usually  effected  by  boiling  with  dilute  sul- 
phuric acid,  though  oxalic  acid  is  used  to  some  extent,  and  phos- 
phoric acid  has  also  been  used.  The  excess  of  acid  is  removed 
bv  treating  the  solutions  with  chalk,  and  filtering.  The  filtered 
solutions  are  evaporated  down  either  to  a  syrupy  consistency, 
and  sent  into  the  market  under  the  names  "glucose,"  "mixing 
syrup/'  etc.,  or  to  dryness,  the  solid  product  being  known  in  com- 
merce as  "grape  sugar."  By  evaporating  the  solutions  down 
to  such  a  concentration  that  the}'  contain  from  12  to  15  per 
cent  of  dextrose,  crystals  are  formed  which  closely  resemble 
those  of  cane  sugar.  They  consist  of  anhydrous  grape  sugar. 
Their  formation  is  facilitated  by  adding  a  little  of  the  crystal- 
lized substance  to  the  concentrated  solutions. 

If  in  the  treatment  of  starch  with  sulphuric  acid  the  trans- 


DEXTROSE.  179 

formation  is  not  complete,  and  this  is  usually  the  case,  the 
product  is  a  mixture  of  dextrose,  maltose,  and  dextrin.  The 
longer  the  action  continues,  the  larger  the  percentage  of 
dextrose. 

Dextrose  crystallizes  from  concentrated  solutions,  usually  in 
crystalline  masses  consisting  of  minute  six-sided  plates.  The 
mass,  as  seen  in  commercial  "  granulated  grape  sugar,"  looks 
very  much  like  granulated  sugar.  It  crystallizes  from  alcohol 
in  mono-clinic  crystals.  It  is  sweet,  but  not  as  sweet  as  cane 
sugar.  According  to  the  latest  estimations,  the  sweetness  of 
dextrose  is  to  that  of  cane  sugar  as  3  to  5.  Its  solutions  turn 
the  plane  of  polarization  to  the  right. 

Dextrose  is  easily  oxidized,  reducing  the  salts  of  silver  and 
copper.  When  treated  with  nascent  hydrogen,  it  yields,  among 
other  products,  mannite  and  hexyl  alcohol.  Under  the  influence 
of  yeast  it  ferments,  yielding  mainly  alcohol  and  carbon  dioxide. 
Putrid  cheese  transforms  it  first  into  lactic  acid  and  then  into 
butyric  acid  by  the  so-called  lactic  acid  fermentation. 

Dextrose  forms  compounds  with  metals  and  salts.  Among 
the  better  known  compounds  of  this  kind  are  those  mentioned 
below :  — 

Sodium  dextrose  ....     C6HnO6 .  Na ; 

Sodium  chloride  dextrose     .  2  C6H12O6 .  NaCl  -f-  H2O  ; 

also,  C6H12O6.NaCl  +  £  H2O,  and  C6H12O6 . 2  NaCl.  These 
compounds,  with  sodium  chloride,  crystallize  well,  and  can  be 
easily  obtained  in  pure  condition. 

Cupric  oxide  dextrose     .     .     C6H12O6.  5  CuO. 

By  treatment  with  acetic  anhydride,  dextrose  yields  a  product 
containing  five  acetyl  groups,  pent-acetjl-dextrose, 

C6H7(C2H30)506. 

NOTE  FOR  STUDENT.  —  What  does  the  formation  of  this  compound 
indicate? 


180  CARBOHYDRATES. 

It  is  often  important  to  know  the  quantity  of  dextrose  con- 
tained in  a  given  liquid  ;  as,  for  example,  in  the  urine  in  a  case 
of  suspected  diabetes.  For  the  purpose  of  making  the  estima- 
tion, advantage  is  taken  of  the  action  of  dextrose  towards  an 
alkaline  solution  of  copper  sulphate.  The  solution  commonly 
used  is  that  known  as  Felilincfs  solution.  It  is  prepared  by 
dissolving  34.64g  crystallized  pure  copper  sulphate  in  water, 
adding  a  solution  of  200g  potassium  sodium  tartrate,  and  600g 
to  700g  caustic  soda  of  the  specific  gravity  1.12,  and  diluting 
so  that  the  whole  makes  one  litre. 

Experiment  38.  Make  half  the  quantity  of  Fehling's  solution 
above  mentioned,  and  put  in  a  bottle  with  a  glass  stopper.  In  a  test- 
tube  boil  about  10CC  of  this  solution,  and  then  add  a  few  drops  of  a 
dilute  solution  of  glucose.  Continue  to  boil,  and  add  a  little  more  of 
the  glucose  solution  ;  and  so  on,  until,  on  removing  the  tube  from  the 
lamp,  a  dark-red  uniform-looking  precipitate  settles,  leaving  the  liquid 
above  it  perfectly  clear  and  colorless.  This  precipitate  is  cuprous 
oxide.  By  taking  proper  precautions,  the  exact  amount  of  dextrose 
present  in  a  solution  may  be  estimated  in  this  way. 

Regarding  the  relation  between  mannite  and  dextrose  we  have 
not  much  positive  knowledge.  The  fact  that  dextrose  so  readily 
reduces  metallic  salts,  and  is  converted  into  mannite  by  reduc- 
tion, has  led  to  the  belief  that  it  is  an  aldehyde  of  mannite,  as 

CH2OH 
1 
represented  by  the  formula  (CHOH)4,  the  corresponding  alcohol 


or  mannite  being  (CHOH)4.     While  dextrose  is  converted  into 

CH2OH 

mannite  by  reduction,  mannite  is  not  converted  into  dextrose 
by  oxidation.  Both  substances  are  converted  into  saccharic 
acid  by  oxidizing  agents,  the  relations  between  the  three  sub- 
stances being  shown  by  the  formulas 


LEVULOSE.  181 

CH2OH  CH2OH  CO,H 

I  I  I 

(CHOH)4  (CHOH)4  (CHOH)4. 

I  I  I 

CH2OH  COH  CO2H 

Mannite.  Dextrose.  Saccharic  acid. 

Levulose  (fruit  sugar),  C6H12Oo.  —  As  has  been  stated, 
levulose  occurs  together  with  dextrose,  and  in  equivalent  quanti- 
ties, in  fruits  ;  and  is  formed  by  the  action  of  dilute  mineral 
acids,  or  ferments  on  cane  sugar,  this  last  breaking  up  accord- 
ing to  the  equation,  — 


+  H20  =  C6H1206 

Cane  sugar.  Dextrose.  Levulose. 

As  cane  sugar  is  found  in  unripe  fruits,  it  is  probable  that 
the  change  represented  by  the  above  equation  takes  place  in  the 
process  of  ripening. 

Levulose  does  not  solidify,  but  forms  a  thick  syrup.  It  is 
about  as  sweet  as  cane  sugar.  It  turns  the  plane  of  polarization 
to  the  left. 

NOTE  FOR  STUDENT.  —  What  other  substances  already  considered 
bear  to  each  other  the  same  relations  as  dextrose  and  levulose? 

It  acts  towards  Fehling's  solution  the  same  as  dextrose.  By 
nascent  hydrogen  it  is  reduced  to  mannite  ;  and  by  oxidizing 
agents  it  is  converted  into  saccharic  acid. 

The  same  arguments  which  lead  to  the  belief,  that  dextrose 
bears  to  mannite  the  relation  of  an  aldehyde  to  an  alcohol, 
lead  also  to  the  conclusion  that  levulose  bears  the  same 
relation  to  mannite.  At  present  we  do  not  know  what  is 
the  cause  of  the  isomerism  of  dextrose  and  levulose.  Though 
the  same  hypothesis  that  was  explained  in  connection  with 
the  two  lactic  acids  may  be  applied  also  in  this  case,  as 
the  formula  representing  dextrose  and  levulose  as  aldehydes 


182  CARBOHYDRATES. 

of  manuite  show  that  each  contains  an  asymmetrical  carbon, 

thus :  — 

COH 
I 

HO-C-H 
I 

CH.OH 
I 
(CHOH)2 

CH2OH 

Galactose,  C6H12O6.  —  This  substance  is  formed  together 
with  dextrose  when  either  sugar  of  milk  or  gum  arabic  is  boiled 
with  dilute  sulphuric  acid. 

It  crystallizes  in  large  rhombic  prisms,  which  melt  at  130° ; 
is  easily  soluble  in  hot  water,  but  much  less  so  in  cold  water ; 
less  sweet  than  cane  sugar ;  turns  the  plane  of  polarization  to 
the  left ;  conducts  itself  in  some  respects  like  dextrose.  It 
reduces  Fehling's  solution ;  gives  mucic  acid  with  nitric  acid, 
and  dulcite  with  sodium  amalgam.  It  does  not  ferment  with 
yeast. 

THE  CANE-SUGAR  GROUP,  C12H22On. 

Cane  sugar,  dzH^Ou.  —  This  well-known  variety  of  sugar 
occurs  very  widely  distributed  in  nature,  in  sugar  cane,  sorghum, 
the  Java  palm,  the  sugar  maple,  beets,  madder  root,  coffee, 
walnuts,  hazel  nuts,  sweet  and  bitter  almonds  ;  in  the  blossoms 
of  many  plants  ;  in  honey,  etc.,  etc. 

It  is  obtained  mainly  from  the  sugar  cane  and  from  beets. 
In  either  case  the  processes  of  extraction  and  refining  are  largely 
mechanical.  When  sugar  cane  is  used,  this  is  macerated  with 
water  to  dissolve  the  sugar.  Thus  a  dark-colored  solution  is 
obtained.  This  is  evaporated,  and  then  passed  through  filters 
of  bone-black  which  remove  the  coloring  matter.  The  solu- 
tion is  evaporated  in  the  air  to  some  extent,  and  then  in 
large  vessels  called  u  vacuum  pans,"  from  which  the  air  is 


CANE   SUGAK.  183 

partly  exhausted,  so  that  the  boiling  takes  place  at  a  lower 
temperature  than  would  be  required  under  the  ordinary  pres- 
sure of  the  atmosphere.  The  mixture  of  crystals  and  mother 
liquors  obtained  from  the  ' '  vacuum  pans "  is  freed  from  the 
liquid  by  being  brought  into  the  "centrifugals."  These  are 
funnel- shaped  sieves  which  are  revolved  very  rapidly,  the  liquid 
being  thus  thrown  by  centrifugal  force  through  the  openings 
of  the  sieve,  while  the  crystals  remain  behind  and  are  thus 
nearly  dried.  The  final  drying  is  effected  by  placing  the  crys- 
tals in  a  warm  room. 

When  beets  are  used  the  process  is  essentially  the  same, 
though  there  are  some  differences  in  the  details. 

The  mother  liquors  which  are  obtained  from  the  ' '  centrif- 
ugals "  are  further  evaporated,  and  yield  lower  grades  of  sugar ; 
and,  finally,  a  syrup  is  obtained  which  does  not  crystallize. 
This  is  molasses.  Molasses  is  sometimes  brought  into  the 
market  as  such ;  sometimes,  particularly  when  obtained  from 
beet  sugar,  it  is  allowed  to  ferment  for  the  purpose  of  making 
alcohol.  The  spent  wash,  or  waste  liquor,  "  vinasse,"  is  now 
evaporated  to  dryness  and  calcined  for  the  purpose  of  getting 
the  alkaline  salts  contained  in  the  residues.  The  products  of 
distillation  are  collected,  and  from  them  are  separated  methyl 
alcohol  and  tri-methyl-amine  (see  p.  96). 

Sugar  crystallizes  from  water  in  well-formed,  large  mono- 
clinic  prisms.  It  is  dextro-rotatory.  When  heated  to  210°  to 
220°,  cane  sugar  loses  water,  and  is  converted  into  the  substance 
called  caramel,  which  is  more  or  less  brown  in  color,  according 
to  the  duration  of  the  heating  and  the  temperature  reached. 
Boiled  with  dilute  acids,  cane  sugar  is  split  into  equal  parts 
of  dextrose  and  levulose,  as  has  been  stated.  The  mixture  of 
the  two  is  called  invert-sugar.  The  process  is  called  inversion. 
It  takes  place,  to  some  extent,  when  impure  sugar  is  allowed 
to  stand.  Hence  invert-sugar  is  contained  in  the  brown  sugars 
found  in  the  market.  Yeast  gradually  transforms  cane  sugar 
into  dextrose  and  levulose,  and  these  then  undergo  fermenta- 
tion. Cane  sugar  itself  does  not  ferment. 


184  CARBOHYDRATES. 

Experiment  39.  Arrange  two  pieces  of  apparatus  as  in  Exp.  7. 
In  one  put  40s  to  oQs  grape  sugar  and  a  certain  quantity  of  yeast,  a? 
in  Exp.  7;  in  the  other  put  the  same  amount  of  cane  sugar  and  of 
yeast.  Notice  the  difference. 

Cane  sugar  does  not  reduce  an  alkaline  solution  of  copper 
sulphate. 

Experiment  4O.  Prepare  a  dilute  solution  of  cane  sugar  by  dis- 
solving is  to  2s  in  200CC  water.  Test  this  with  Fehling's  solution, 
as  in  Exp.  38.  Now  add  to  the  sugar  solution  10  drops  concentrated 
hydrochloric  acid,  and  heat  for  half  an  hour  on  the  water-bath  at 
100°;  exactly  neutralize  the  acid  with  a  dilute  solution  of  sodium 
carbonate,  and  test  with  Fehling's  solution. 

Oxidizing  agents  readily  convert  cane  sugar  into  oxalic  acid 
(see  Exp.  34)  and  saccharic  acid. 

Like  dextrose,  cane  sugar  forms  compounds  with  metals, 
metallic  oxides,  and  salts.  Among  these  the  following  may 
be  mentioned :  — 

Sodium  sucrate      ....  C12H2iOn .  Na, 

Sodium-chloride  s ucr ate  .     .  C12H22On.  NaCl, 

Calcium  sucrate      ....  C12H20On .  Ca, 

and          Lime  sucrate C12H22On.  2  CaO. 

These  derivatives  are  not  sweet. 

An  oct-acetate  of  the  formula  C12H14(C2HSO)8O.:  has  been 
made  by  treating  sugar  with  sodium  acetate  and  acetic  anhy- 
dride. 

Though  cane  sugar  readily  breaks  up  into  dextrose  and  levu- 
lose,  no  one  has  succeeded  as  yet  in  effecting  the  union  of  these 
two  substances  to  form  cane  sugar.  The  character  of  the 
relation  between  it  and  the  two  glucoses  is  not  understood. 

Sugar  of  milk,  lactose,  C^H^On  +  H2O.  —  This  sugar 
occurs  in  the  milk  of  all  mammals.  It  is  obtained  in  the  manu- 
facture of  cheese.  The  casern  is  separated  from  the  milk  by 


CELLULOSE,  185 

means  of  rennet.  The  sugar  of  milk  remains  in  solution,  is 
separated  by  evaporation,  and  purified  b}-  recrystallization.  It 
crystallizes  in  rhombic  crystals.  That  which  comes  into  the 
market  has  been  crystallized  on  strings  or  wood  splinters.  It 
has  a  slightly  sweet  taste ;  is  much  less  soluble  in  water  than 
cane  sugar,  and  is  dextro-rotatory.  It  reduces  Fehling's  solu- 
tion. Oxidized  with  nitric  acid,  it  yields  mucic  and  saccharic 
acids.  Nascent  hydrogen  converts  sugar  of  milk  into  mannite, 
dulcite,  and  other  substances.  Like  dextrose  and  cane  sugar, 
it  forms  compounds  with  bases,  dissolving  lime,  baryta,  lead 
oxide,  etc. 

Sugar  of  milk  ferments  under  certain  circumstances,  and 
is  thus  converted  into  lactic  acid.  The  souring  of  milk  is  a 
result  of  this  fermentation.  The  lactic  acid  formed  coagulates 
the  casein  ;  hence  the  thickening. 

Maltose,  C^H^On.  —  This  carbohydrate  is  formed  by  the 
action  of  malt  on  starch.  Malt,  which  is  made  by  steeping 
barley  in  water  until  it  germinates,  and  then  drying  it,  contains 
a  substance  called  diastase,  which  has  the  power  of  effecting 
changes  similar  to  some  of  those  effected  by  the  ferments. 
Thus,  it  acts  upon  starch,  and  converts  it  into  dextrin  and 
maltose :  — 

3  C6H1005  +  H20  =  C12H22On  +  C6HI005. 

Starch.  Maltose.  Dextrin. 

Maltose  is  also  formed  by  the  action  of  dilute  sulphuric  acid 
upon  starch,  and  is  hence  contained  in  commercial  glucoses. 
By  further  treatment  with  sulphuric  acid  it  is  converted  into 
dextrose.  Maltose  crystallizes  in  fine  needles  ;  is  dextro-rota- 
tory ;  reduces  Fehling's  solution,  and  ferments  with  yeast. 

THE  CELLULOSE  GROUP,  C6H10O5. 

Cellulose,  CtiH]0Oo.  —  Cellulose  forms,  as  it  were,  the  ground 
work  of  all  vegetable  tissues.  It  presents  different  appearances 
and  different  properties,  according  to  the  source  from  which  it 


186  CARBOHYDRATES. 

is  obtained ;  but  these  differences  are  due  to  substances  with 
•which  the  cellulose  is  mixed ;  and  when  they  are  removed,  the 
cellulose  left  behind  is  the  same  thing,  no  matter  what  its  source 
may  have  been.  The  coarse  wood  of  trees,  as  well  as  the  ten- 
der shoots  of  the  most  delicate  plants,  all  contain  cellulose  as 
an  essential  constituent.  It  forms  the  membrane  of  the  cells. 
Cotton-wool,  hemp,  and  flax  consist  almost  wholly  of  cellulose. 
For  the  preparation  of  cellulose,  either  Swedish  filter-paper 
or  cotton- wool  may  be  taken. 

Experiment  41.  Treat  some  cotton-wool  successively  with  ether, 
alcohol,  water,  a  caustic  alkali,  and,  finally,  a  dilute  acid.  Then  wash 
with  water. 

Cellulose  is  amorphous  ;  insoluble  in  all  ordinary  solvents  ; 
soluble  in  an  ammoniacal  solution  of  cupric  oxide. 

Experiment  42.  Add  some  ammonium  chloride  to  a  solution  of 
copper  sulphate;  precipitate  with  caustic  soda;  filter,  and  carefully 
wash.  Dissolve  the  cupric  hydroxide  thus  obtained  in  ammonia.  The 
solution  is  known  as  Schweizer's  reagent.  It  will  dissolve  cellulose. 
Try  it  with  some  of  the  cellulose  obtained  in  Exp.  41. 

Cellulose  dissolves  in  concentrated  sulphuric  acid.  If  the 
solution  be  diluted  and  boiled,  the  cellulose  is  converted  into 
dextrin  and  dextrose.  It  will  thus  be  seen  that  rags,  which 
consist  largely  of  cellulose,  paper,  and  wood,  might  be  used 
for  the  preparation  of  dextrose  or  glucose,  and  consequently 
of  alcohol. 

Gun  cotton,  pyroxylin,  nitre-cellulose.  —  Cellulose  has 
some  of  the  properties  of  alcohols  ;  among  them  the  power  to 
form  ethereal  salts  with  acids.  Thus,  when  treated  with  nitric 
acid,  it  forms  several  nitrates,  just  as  glycerin  forms  the  nitrates 
known  as  nitro-glycerin  (which  see) . 

Treated  for  a  short  time  with  sulphuric  and  nitric  acids, 
cellulose  is  converted  into  the  lower  nitrates,  particularly  the 


STARCH.  187 

tetra-  and  penta-nitrates.  A  solution  of  these  in  a  mixture  of 
ether  and  alcohol  is  known  as  collodion  solution,  which  is  much 
used  in  photography.  When  poured  upon  any  surface,  such  as 
glass,  the  ether  and  alcohol  rapidly  evaporate,  leaving  a  thin 
coating  of  the  nitrates  which  were  in  solution. 

When  treated  for  twenty-four  hours  at  10°  with  a  mixture 
of  nitric  and  sulphuric  acids,  cellulose  yields  the  hexa-nitrate 
C12H14O4(O.  NO2)6,  which  is  used  as  an  explosive  under  the 
name  of  gun  cotton.  It  is  used  chiefly  for  blasting. 

An  intimate  mixture  of  gun  cotton  and  camphor  has  come 
into  extensive  use  under  the  name  of  celluloid.  As  it  is  plastic 
at  a  slightly  elevated  temperature,  it  can  easily  be  moulded  into 
any  desired  shape.  When  it  cools  it  hardens. 

Paper.  —  Paper  in  its  many  forms  consists  mainly  of  cellu- 
lose. The  essential  features  in  the  manufacture  of  paper  are, 
first,  the  disintegration  of  the  substances  used.  This  is  effected 
partly  mechanically,  and  partly  b}'  boiling  with  caustic  soda. 
The  mass  is  converted  into  pulp  by  means  of  knives  placed  on 
rollers.  The  pulp,  with  the  necessary  quantity  of  water,  is 
then  passed  between  rollers.  Chiefly  rags  of  cotton  or  linen 
are  used  in  the  manufacture  of  paper;  wood  and  straw  are 
also  used. 

Starch,  C6H10O5.  —  Starch  is  found  everywhere  in  the  vege- 
table kingdom  in  large  quantity,  particularly  in  all  kinds  of 
grain,  as  maize,  wheat,  etc.  ;  in  tubers,  as  the  potato,  arrow- 
root, etc.  ;  in  fruits,  as  chestnuts,  acorns,  etc. 

In  the  United  States  starch  is  manufactured  mainly  from 
maize  ;  in  Europe,  from  potatoes. 

The  processes  involved  in  the  manufacture  of  starch  are 
mostly  mechanical.  The  maize  is  first  treated  with  warm 
water ;  the  softened  grain  is  then  ground  between  stones,  a 
stream  of  water  running  continuously  into  the  mill.  The  thin 
paste  which  is  carried  away  is  brought  upon  sieves  of  silk  bolt- 


188  CARBOHYDRATES. 

ing-cloth,  which  are  kept  in  constant  motion.  The  starch  passes 
through  with  the  water  as  a  milky  fluid.  This  is  allowed  to 
settle  when  the  water  is  drawn  oft'.  The  starch  is  next  treated 
with  water  containing  a  little  alkali  (caustic  soda,  or  sodium 
carbonate),  the  object  of  which  is  to  dissolve  gluten,  oil,  etc. 
The  mixture  is  now  brought  into  shallow,  long  wooden  runs, 
where  the  starch  is  deposited,  the  alkaline  water  running  off. 
Finally,  the  starch  is  washed  with  water,  and  dried  at  a  low 
temperature. 

Starch  has  a  granular  structure,  the  grains  as  seen  under  the 
microscope  having  a  series  of  concentric  markings,  of  which  the 
nucleus  appears  to  be  at  one  side. 

Starch  in  its  usual  condition  is  insoluble  in  water.  If  ground 
with  cold  water,  it  is  partly  dissolved.  If  heated  with  water, 
the  membranes  of  the  starch-cells  are  broken,  and  the  contents 
form  a  partial  solution.  On  cooling,  it  forms  a  transparent 
jelly  called  starch  paste. 

With  iodine,  starch  paste  gives  a  deep  blue  color ;  with  bro- 
mine, a  yellow  color. 

Experiment  43.  Make  some  starch  paste  thus :  Put  a  few  grams 
of  starch1  in  an  evaporating  dish ;  pour  enough  cold  water  upon  it  to 
cover  it ;  grind  it  under  the  water  with  a  pestle,  and  then  pqur  200CC  to 
300CC  hot  water  upon  it.  When  this  is  cool,  add  a  few  drops  to  a  litre 
of  water,  and  then  add  a  few  drops  of  potassium  iodide.  As  long  as 
the  iodine  is  in  combination  with  the  potassium  no  change  of  color 
takes  place;  but  if  the  iodine  be  set  free  by  the  addition  of  a  drop  or 
two  of  chlorine  water,  or  of  strong  nitric  acid,  the  entire  liquid  turns 
a  beautiful  dark  blue.  The  cause  of  this  color  is  the  formation  of  a 
very  unstable  compound  of  starch  and  iodine.  The  color  is  easily 
destroyed  by  a  slight  excess  of  chlorine  water  (try  it  in  a  test-tube) ; 
by  alkalies  (try  it)  ;  by  sulphurous  acid  (try  it)  ;  by  hydrogen  sulphide 
(try  it)  ;  etc.  It  is  also  destroyed  by  heating.  (Heat  some  of  the 
solution  in  a  test-tube,  and  let  it  stand.)  The  color  reappears  on 
cooling. 

1  The  purest  form  of  starch  to  be  found  in  the  market  is  that  made  from  arrow-root. 
Ordinary  starch  contains  other  substances  which  sometimes  interfere  with  the  reactions. 


GUMS.  189 

Experiment  44.  Use  some  of  the  starch  paste  in  studying  the 
effect  of  bromine  upon  it.  Use  dilute  solutions.  The  bromine  must 
be  in  the  free  condition. 

It  has  been  stated  that  starch  is  converted  into  dextrin,  mal- 
tose, and  dextrose  by  dilute  acids  ;  and  that  diastase  converts 
it  into  maltose  and  dextrin. 

Experiment  45.  Add  20CC  concentrated  hydrochloric  acid  to  200CC 
of  the  starch  paste  already  made,  and  heat  for  two  hours  on  the  water- 
bath,  connecting  the  flask  with  an  inverted  condenser  (see  Fig.  8). 
Then  examine  with  Fehling's  solution.  Test,  also,  some  of  the  original 
starch  paste  with  Fehling's  solution. 

Dextrin,  C6H10O5.  —  Dextrin,  as  has  been  stated,  is  formed 
by  treating  starch  with  dilute  acids  or  diastase.  It  is  converted 
by  further  treatment  with  acids  into  dextrose.  The  substance 
ordinarily  called  dextrin  has  been  shown  to  be  a  mixture  of 
several  isomeric  substances  which  resemble  each  other  very 
closely.  The  mixture  is  an  uncrystallizable  solid.  It  is 
strongly  dextro-rotatory ;  gives  a  red  color  with  iodine  and 
does  not  reduce  Fehling's  solution.  It  is  used  extensively  as 
a  substitute  for  gum. 

Gums.  —  Under  this  head  are  included  a  number  of  sub- 
stances which  occur  in  nature.  One  of  the  best  known  is  gum 
arable,  which  is  obtained  in  Senegambia  from  the  bark  of  trees 
belonging  to  the  Acacia  variety.  Its  formula,  like  that  of  cane 
sugar,  is  C^H^On-  Other  gums  are  wood  gum,  obtained  from 
the  birch,  ash,  beech,  etc.  ;  bassorin,  the  chief  constituent  of 
gum  tragacanth,  etc. 

Our  knowledge  of  the  chemistry  of  these  gums  is  very  limited. 


CHAPTER    XII. 
MIXED   COMPOUNDS   CONTAINING-   NITROGEN. 

IN  speaking  of  the  preparation  of  bibasic  acids  from  mono- 
basic acids,  reference  was  made  to  cyan-acetic  and  the  two 
cyan-propionic  acids.  These  are  nothing  but  simple  cyanogen 
substitution-products  analogous  to  chlor-acetic  and  the  two 
chlor-propionic  acids.  They  are  made  by  treating  the  chlorine 
products  with  potassium  cyanide.  They  have  been  useful 
chiefly  in  the  preparation  of  bibasic  acids,  as  described  in  con- 
nection with  malonic  and  the  two  succinic  acids.  It  will  there- 
fore not  be  necessary  to  consider  them  individually  here. 

NOTE  FOR  STUDENT.  —  How  may  malonic  be  made  from  acetic  acid ; 
and  the  two  succinic  acids  from  propionic  acid  ?  Give  the  equations. 

The  chief  substances  to  be  considered  under  the  head  of 
mixed  compounds  containing  nitrogen  are  the  amido-acids  and 
the  acid  amides.  As  will  be  seen,  both  these  classes  of  sub- 
stances are  of  special  interest,  as  they  represent  forms  of  com- 
bination which  are  favorite  ones  in  nature,  especially  in  the 
animal  kingdom,  some  of  the  most  important  substances  found 
in  the  animal  body,  such  as  urea,  uric  acid,  glycocoll,  etc., 
belonging  to  one  or  both  the  classes. 

AMIDO-ACIDS. 

The  relation  of  an  amido-acid  to  the  simple  acid  is,  as  the 
name  implies,  the  same  as  that  of  an  amido  derivative  of  a 
hydrocarbon  to  the  hydrocarbon.  That  is  to  say,  it  may  be 
regarded  as  the  acid  in  which  a  hydrogen  is  replaced  by  the 
amido  group,  NH2.  Thus,  amido-acetic  acid  is  represented 


AMIDOFOBMIC   ACID.  191 

by  the  formula  CH2  <       2    ;  while  amido-me  thane,  or  methyl- 

\^\JnfL 

amine  is  represented  thus,  CH3  .  NH2.  The  reasons  for  regard- 
ing methyl-amine  as  a  substituted  ammonia,  as  represented, 
have  been  stated.  The  formula  is  based  upon  the  reactions 
of  the  substance  ;  that  is,  upon  its  chemical  conduct  and  the 
methods  used  in  its  preparation.  The  same  arguments  might 
be  advanced  in  favor  of  the  view  that  the  amido-acids  are 
substituted  ammonias,  and,  at  the  same  time,  acids.  The 
simplest  method  for  their  preparation  consists  in  treating 
halogen  derivatives  of  the  acids  with  ammonia  ;  thus  amido- 
acetic  acid  may  be  made  b}-  treating  brom-acetic  acid  with 
ammonia  :  — 


NOTE  FOR  STUDENT.  —  Compare  this  reaction  with  that  made  use 
of  for  making  methyl-amine. 

NH, 

Amido-formic  acid,  carbamic  acid,    I          .  —  This  acid 

CO2H 

is    not   known    in    the    free    condition.       Its    ammonium    salt, 
NH2 

I  ,    is   formed   when  carbon   dioxide   and   ammonia   are 

C02NH4 

brought  together  :  — 

NH2 
I 
CO2  +  2  NH3  =  CO2NH4. 

The  other  carbamates  may  be  prepared  from  the  ammonium 
salt.  "  They  are  decomposed,  yielding  carbonates  and  ammonia. 
Thus,  when  potassium  carbamate  is  warmed  in  water  solution, 
decomposition  takes  place,  as  represented  in  the  equation,  — 


NH2.CO2K  +  H2O  =  NH3  +  HKCO3. 
The   ethereal   salts   of   carbamic    acid   are   readily  made  by 


192         MIXED   COMPOUNDS   CONTAINING  NITROGEN. 

treating  the  ethereal  salts  of  chlor-formic  acid  (see  p.  157) 
with  ammonia :  — 

Cl  NH9 

I  I 

CO2C2H5  +  2  NH3  =  COAH,  +  NH4C1. 

Amido-formic  acid  cannot  be  taken  as  a  fair  representative 
of  the  amido-acids,  any  more  than  carbonic  acid  can  be  taken 
as  a  fair  representative  of  the  hydroxy-acids. 

Glycocoll,  glycine,  >  /  NH2 

.  ,  , .  .  ,    (  U2±i5JNU2   —  O±i2  <.  n,^  TT 

amido-acetic   acid,  )  V  OO2H 

bile  are  contained  two  complicated  acids,  which  are  known  as 
glycocholic  and  taurocholic  acids.  When  glycocholic  acid  is 
boiled  with  hydrochloric  acid,  it  breaks  up,  yielding  cholic  acid 
and  glycocoll.  In  the  urine  of  horses  is  found  an  acid  known 
as  hippuric  acid.  When  this  is  boiled  with  hydrochloric  acid, 
it  breaks  up  into  benzoic  acid  and  glycocoll. 

When  uric  acid  is  treated  with  hydriodic  acid,  glycocoll  is 
one  of  the  products.  Further,  glycocoll  is  formed  when  glue 
is  boiled  with  baryta  water  or  dilute  sulphuric  acid.  Its  forma- 
tion from  brom-acetic  acid  and  ammonia,  mentioned  above,  gives 
the  clearest  indication  in  regard  to  its  relation  to  acetic  acid. 

Amido-acetic  acid  has  both  acid  and  basic  properties.  It 
unites  with  acids,  forming  weak  salts  ;  and  it  acts  upon  bases, 
giving  salts  with  metals, — the  amido-acetates.  It  also  unites 
with  salts,  forming  double  compounds. 

Examples  of  the  compounds  with  acids  are  the 

Hydrochloride  .     .     .     .     CH-' <  n^*101' 

and  the    Nitrate CH2  <  ^2  *  HN°3 ; 

CO2H 

of  the  salts  with  metals, 

Zinc  amido-acetate     .     ,     Zn(C2H4NO2)2  -f-  H2O, 
and          Copper  amido-acetate      .     Cu(C2H4NO2)2-j- H2O ; 


AMIDO-PROPION1C   ACIDS.  193 

of  the  compounds  with  salts,  the  double  salt  of 

Copper  nitrate  j  Cu(No3)2.Cu(C2H4NO2)2+  2  HaO. 

and  Copper  amido-acetate,  ) 

Treated  with  nitrous  acid,  glycocoll  is  converted  into  hydroxy- 
acetic  acid. 

NOTE  FOR  STUDENT.  —  Write  the  equation  representing  the  reaction 
which  takes  place  when  glycocoll  is  treated  with  nitrous  acid. 


Sarcosine,  methyl-glycocoll,  O 

If  brom-acetic  acid  be  treated  with  metlryl-ainine  instead  of 
with  ammonia,  a  reaction  takes  place  similar  to  that  which  takes 
place  with  ammonia,  the  product  being  methyl  glycocoll  or  sarco- 

sine  :  — 

CHs  <  rn  TI  +  2  NHa          =  CH*  <  rn  w  +  NH*Br  ;  and 
UUgH  UUfU 

CHs  <  rn  TT  +  2  CH3'  NHs  =  CH*  <  rn  w  !Hs  +  NH3(CH3)Br. 

CU2U  CU2H 

Sarcosine. 

Sarcosine  is  a  product  of  the  decomposition  of  creatine,  which 
is  found  in  meat,  and  of  caffeine,  which  is  a  constituent  of  coffee 
and  tea.  It  is  obtained  from  creatine  and  caffeine  by  boiling 
them  with  baryta  water. 

Its  properties  are  much  like  those  of  glycocoll. 

Amido-propionic  acids,  C..H7NO2.  —  These  acids  bear  to 
propionic  acid  relations  similar  to  that  which  amido-acetic  acid 
bears  to  acetic  acid.  There  are  two,  corresponding  to  a-  and 
/2-chlor-propionic  acids,  from  which  they  are  made.  They  are 
not  found  in  nature.  Their  properties  are  much  like  those  of 
glycocoll. 

NOTE  FOR  STUDENT.  —  What  substances  would  be  formed  by  treat- 
ing the  two  araido-propionic  acids  with  nitrous  acids? 

Among  the  amido  derivatives  of  the  higher  members  of  the 


194        MIXED   COMPOUNDS   CONTAINING  NITROGEN. 

fatty  acid  series,  that  of  caproic  acid  should  be  specially  men- 
tioned. 

Leucine,  a-amido-caproic  acid, 

CeH13NOa  [=CHs .  CH2 .  CH2 .  CH2 .  CH(NH2) .  CO2H  ] . 
Leucine  is  found  very  widely  distributed  in  the  animal  kingdom, 
as  in  the  spleen,  pancreas,  and  brain.  It  has  also  been  found 
in  the  vegetable  kingdom  in  a  few  plants.  It  is  produced  by 
the  decomposition  of  substances  containing  albumin  or  gelatin. 
It  has  been  made  by  treating  a-brom-caproic  acid  with  ammonia. 

AMIDO-SULPHONIC  ACIDS. 

Just  as  there  are  amido  derivatives  of  the  carbonic  acids, 
so,  too,  there  may  be  amido  derivatives  of  the  sulphonic  acids. 
Only  one  of  these  need  be  considered. 

Taurine,  \  f  SO3H 

Amido-isethionic  acid,    I  '°V      H4<NH3 

Taurine  is  found  in  combination  with  cholic  acid  in  taurocholic 

acid,  in  ox  bile  and  the  bile  of  many  animals,  as  well  as  in 

other   animal  liquids.      It   has  been  made  synthetically  from 

OTT 

isethionic  acid,  C2IL  <  0    TT,  by  treating  the  acid  successively 
hO3H 

with  phosphorus  pentachloride  and  ammonia :  — 
C •*  <  S?2OH  +  2  PC1'  -  ° A  <  S02C1  + 

Isethionic  acid.  Chlor-ethyl-sulpho-chloride. 


Chlor-ethyl-sulphonic  acid. 

C2H4  <  ^  ,    T  +  2  NH3  =  C2H4  <  *[?*    +  NH4C1. 


Taurine. 


Taurine  crystallizes  in  large  tetragonal  prisms.  It  is  a  very 
stable  substance,  and  can  be  boiled  with  concentrated  acids  with- 
out decomposition.  With  nitrous  acids  it  yields  isethionic  acid. 

It  unites  with  bases  forming  salts. 


ACID   AMIDES.  195 

The  only  amido-bibasic  acid  which  need  be  considered  is 
amido-succinic  acid. 

Aspartic  acid,  i  /  CO2 

.  .  .    .  .  ,     f  O4±iTJNU4  =  U2Jt±3(.N.H.2)  <.  ~n 

Amido-succinic  acid,  J  V  CO2. 

Aspartic  acid  occurs  in  pumpkin  seeds,  and  is  frequently 
met  with  as  a  product  of  boiling  various  natural  compounds 
with  dilute  acids.  Thus,  for  example,  it  is  formed  when  casein 
and  albumin  are  treated  in  this  wa}~.  It  is  formed  also  when 
asparagine  (which  see)  is  boiled  with  acids  or  alkalies. 

Aspartic  acid  eiystallizes.  It  turns  the  plane  of  polarization , 
under  some  circumstances  to  the  right,  under  others  to  the  left. 

Treated  with  nitrous  acids  it  yields  malic  acid. 

ACID  AMIDES. 

When  the  ammonium  salt  of  acetic  acid  is  heated,  it  gives  off 
water,  and  a  body  distils  over  which  is  known  as  acetamide. 
The  reaction  which  takes  place  is  represented  by  the  following- 
equation  :  — 

CH3.COONH4  =  CH3.CONH2  +  H2O. 

The  substance  obtained  has  neither  acid  nor  basic  properties. 
An  examination  of  the  ammonium  salts  of  other  acids  shows 
that  the  reaction  is  a  general  one,  and  we  thus  may  get  a  class 
of  neutral  bodies,  known  as  the  acid  amides. 

As  no  one  of  the  acid  amides  of  the  fatty  acid  series  is  of 
special  importance,  a  few  words  of  a  general  character  in  regard 
to  the  class  will  suffice. 

Besides  the  reaction  above  referred  to  for  making  the  acid 
amides,  there  are  two  others  of  general  application.  One  con- 
sists in  treating  an  ethereal  salt  of  an  acid  with  ammonia ; 
thus,  when  ethyl  acetate  is  treated  with  ammonia,  this  reaction 
takes  place :  — 

CH3.CO2C2H5  +  NH3  =  CH3.CONH2  +  C2H6O. 


196         MIXED   COMPOUNDS    CONTAINING   NITROGEN. 

The  other  reaction  consists  in  treating  the  acid  chlorides  with 
ammonia.  Thus,  to  get  acetamide,  we  may  treat  acetyl  chloride 
(see  p.  61)  with  ammonia  :  — 

CH3.COC1  +  2NH3  =  CH3.CONH2  +  NH4C1. 

This  last  reaction  is  perhaps  used  most  frequently.  It  shows 
the  relation  which  exists  between  acetic  acid  and  acetamide. 
For  acetyl  chloride  is  made  from  acetic  acid  by  treatment  with 
phosphorus  trichloride,  and  is,  therefore,  as  has  been  pointed 
out,  to  be  regarded  as  acetic  acid  in  which  the  hydroxyl  is 
replaced  by  chlorine.  Now,  by  treatment  with  ammonia  the 
same  reaction  takes  place  as  that  which  we  have  had  to  deal 
with  in  the  preparation  of  amido-acids,  the  chlorine  is  replaced 
by  the  amido  group.  Therefore,  acetamide  is  acetic  acid  in 
which  the  hydroxyl  is  replaced  by  the  amido  group,  as  shown 
in  the  formulas  :  — 

O  O 

1  I 

CH3.C-OH  CH3-C-NH2. 

Acetic  acid.  Acetamide. 

As  the  acid  hydrogen  of  the  acid  is  replaced,  the  amide  is  not 
an  acid.  On  the  other  hand,  the  basic  properties  of  the  am- 
monia are  destroyed  by  the  presence  of  the  acid  residue  as  a 
part  of  its  composition.  This  latter  fact  may  be  stated  in 
another  WSLJ  ;  viz.,  when  an  ammonia  residue  is  in  combination 
with  carbon,  which  in  turn  is  in  combination  witji  oxygen,  its 
basic  properties  are  destroyed. 

The  amides  are  converted  into  ammonia  and  a  salt  when 
boiled  with  strong  bases  :  — 

CH3.CONH,  +  KOH  =  CH3CO2K  +  NH3. 

They  are  converted  into  cyanides   by  treatment  with  phos 
phorus  pentoxide  P2O5 :  — 

CH3.CONH2  =  CH3.CN  +  H2O. 

As  the  substance  obtained  in  this  way  is  identical  with  methy: 


ACID   AMIDES. 


197 


cyanide,  which  is  formed  by  treating  methyl-sulphuric  acid  with 
potassium  cyanide,  the  reaction  furnishes  additional  evidence 
in  favor  of  the  conclusion  already  reached;  viz.,  that  in  the 
cyanides  the  carbon  and  not  the  nitrogen  of  the  cyanogen 
group  is  in  combination  with  the  Irydrocarbon  residue,  as  repre- 
sented in  the  formula  CH3— C  — N. 

As  acetamide  is  made  b}'  treating  ammonia  with  the  chloride 
of  acetic  acid,  so,  by  treating  ammonia  with  the  chloride  of  any 
acid,  the  corresponding  amide  may  be  made.  So,  also,  by  treat- 
ing ammonia  with  acid  chlorides,  or  by  treating  acid  amides  with 
strong  acids,  more  complicated  compounds  may  be  obtained. 

fCHO  f0^0 

Of  these  di-acetamide,  NH^  X*Z*X»  and  tri-acetamide,  N-I  C2H,0, 

-CA°  lc2H30 

may  serve  as  examples.     The  relations  of  these  substances  to 

ammonia  and  to  acetic  acid  are  shown  by  the  formulas,  ordinary 
or  mon-acetamide  being  NH2 .  C2H3O  or  CH3 .  CO .  NH2. 


Fig.  12. 

Experiment  46.  Arrange  an  apparatus  as  shown  In  Fig.  12.  In 
flask  A  put  150s  oxalic  acid  (dehydrated  at  100°)  and  100^  absolute 
alcohol ;  and,  in  flask  J5,  100s  absolute  alcohol.  Heat  the  bath  D  to 
100° ;  and  then  heat  the  alcohol  in  flask  B  to  boiling,  and  continue  to 


198         MIXED   COMPOUNDS    CONTAINING   NITKOGEN. 

pass  the  vapor  from  flask  B  into  the  mixture  in  flask  A,  meanwhile 
allowing  the  temperature  of  the  oil-bath  to  rise  to  125°-130°.  A 
mixture  of  alcohol  and  ethyl  oxalate  will  distil  over.  To  some  of  this 
mixture  in  a  flask  add  concentrated  aqueous  ammonia,  and  shake. 
Insoluble  oxamide  is  formed  and  is  thrown  down  as  a  white  powder. 
What  reactions  have  taken  place?  Write  the  equations.  Filter  off 
the  oxamide,  and  wash  it  with  water.  See  whether  it  conducts  itself 
like  an  acid.  Has  it  an  acid  reaction?  Boil  with  caustic  potash  (not 
too  much),  and  notice  whether  ammonia  is  given  off.  Why  does  it 
dissolve?  How  can  the  oxalic  acid  be  extracted  from  the  solution? 

When  the  amide  of  a  poly-basic  acid  is  boiled  with  ammonia, 
and  under  some  other  circumstances,  partial  decomposition 
takes  place,  and  a  substance  is  formed  which  is  both  amide  and 
acid.  Thus,  in  the  case  of  oxamide,  the  product  is  oxamic 

CO2H 
acid,   |  .      This   acid   forms    well-characterized   salts   and 

CONH2 
other  derivatives,  such  as  are  obtained  from  acids  in  general. 

There  is  one  acid  of  this  kind  which  is  a  well-known  natural 
substance.  It  has  already  been  referred  to  in  connection  with 
aspartic  acid,  which  is  closely  related  to  it.  It  is 

Asparagine,  amido-succinamic  acid, 

C4H8N203  +  H2o(=  C2H3(NH2)  <  co^2)-  —  Asparagine  is 
found  in  a  great  many  plants,  as  in  asparagus,  liquorice,  beets, 
peas,  beans,  vetches,  etc.  It  may  be  made  by  treating  mon- 
ethyl  amido-succinate  with  ammonia. 

NOTE  FOR  STUDENT.  —  What  reaction  takes  place?  Write  the  equa- 
tion. 

Asparagine  forms  large  rhombic  crystals,  difficultly  soluble 
in  cold  water,  more  easily  in  hot  water.  When  boiled  with 
acids  or  alkalies,  it  is  converted  into  aspartic  acid  and  ammonia. 

NOTE  FOR  STUDENT.  —  Notice  that  only  the  amido  group  of  the 
amide  is  driven  out  of  the  compound  by  this  treatment.  The  other 
amido  group  which  is  contained  in  the  hydrocarbon  portion  of  the 
compound  is  not  disturbed. 

Nitrous  acid  converts  asparagine  into  malic  acid. 


CEEATINE.  199 

Cyan-amides,  CN2H2. —  In  speaking  of  cyanic  acid,  the 
existence  of  two  chlorides  of  cyanogen  was  mentioned :  one 
a  liquid,  having  the  formula  CNC1 ;  the  other  a  solid,  of  the 
formula  C3N3C13.  When  the  former  is  treated  with  ammonia, 
it  is  converted  into  an  amide,  CN .  NH2,  which  bears  to  cyanic 
acid,  NC.OH,  the  relation  of  an  amide.  Like  the  other 
simple  compounds  of  cyanogen,  cyan-amide  readily  undergoes 
change.  When  simply  kept  unmolested,  it  is  converted  into 
di-cyan-diamide,  C2N4H4;  while,  when  heated  to  150°,  a  violent 
reaction  takes  place,  and  tri-cyan-triamide,  C3N6H6,  is  formed. 
Whether  or  not  the  formulas  given  really  express  the  true 
molecular  weights  of  the  products  is  not  known.  It  can  only 
be  said  that  the  changes  involve  no  change  in  per  centage 
composition,  and  therefore  are  cases  of  polymerisation.  The 
formation  of  the  compounds  is  particularly  interesting,  as  illus- 
trating the  tendency  on  the  part  of  the  simpler  cyanides  to 
undergo  change  under  very  slight  provocation. 

Guanidine,  CN3H5.  —  This  substance,  which  is  closely 
related  to  cyan-amide,  is  formed  by  the  oxidation  of  guanine 
(which  see) ,  and  this  in  turn  is  obtained  from  guano.  It  may 
also  be  made  b}^  treating  c}Tanogen  iodide  with  ammonia :  — 

CNI  +  2NH3  =  CN3H5.HI, 

the  product  being   the  hydriodic  acid  salt  of  guanidine.     As 
will  be  seen,  guanidine  is  cyan-amide  plus  ammonia :  — 
CN .  NH2  +  NH3  =  CN3H5. 

It  is   a  strongly  alkaline  base.     Boiled  with   dilute  sulphuric 
acid  or  baryta  water,  it  yields  urea  and  ammonia  :  — 

CN3H5  +  H20  =  CON2H4  +  NH3. 

Guanidine.  TJrea. 

Creatine,  C4H9N3O2.  —  This  substance  is  found  in  the 
muscles  of  all  animals.  It  is  closely  related  to  guanidine  and 


200         MIXED   COMPOUNDS   CONTAINING   NITROGEN. 

also  to  sarcosine  (see  p.  193).  It  1ms  been  made  synthetically 
by  bringing  cyan-amide  and  sarcosine  together.  The  reaction 
which  takes  place  is  analogous  to  that  made  use  of  for  the 
preparation  of  guanidine.  The  analogy  is  shown  by  the  two 
equations,  — 

CN  .  NH2  +  NH3  =  CN3H5, 

Guanidine. 

or  (CN2H3.NH2), 
(H 

and    CN  .  NH2  +  N  ]  CH3  =  CN2H3  •  N  j  ^* 

(CH2.CO2H        Creatine- 

Sarcosine. 

or  C4H9N3O2. 

Urea,  or  carbamide  and  derivatives.  —  Closely  related 
to  the  nitrogen  compounds  just  considered  is  urea,  or  the 
amide  of  carbonic  acid.  Its  importance  and  certain  peculiari- 
ties distinguish  it  from  the  other  acid  amides,  and  it  is  there- 
fore considered  by  itself. 

Urea  is  found  in  the  urine  and  blood  of  all  mammals,  and 
particularly  in  the  urine  of  carnivorous  animals.  Human 
urine  contains  from  2  to  3  per  cent  ;  the  quantity  given  off  by 
an  adult  man  in  24  hours  being  about  30g.  Urea  may  be  made 
by  the  following  methods  :  — 

(1)  By  treating  carbonyl  chloride  with  ammonia  :  — 

COC12  +  2  NH3  =  CON2H4  +  2  HC1. 
What  is  the  analogous  reaction  for  the  preparation  of  acetamicle? 

(2)  By  heating  ammonium  carbamate  :  — 


What  Is  the  analogous  reaction  for  preparing  oxamide? 
(3)   By  treating  ethyl  carbonate  with  ammonia  :  — 

CO  <  °^H*  +  2  NH3  =  CON2H4  +  2  C2H6O. 


UKEA.  201 

(4)  By  the  addition  of  water  to  cyan-amide  :  — 

CN .  NH2  +  H2O  =  CON2H4. 

(5)  By  evaporation  of  ammonium  cyanate  in  aqueous  solu- 
tion :  — 

CN(ONH4)  =  CON2H4. 

This  reaction  is  of  special  interest,  for  the  reason  that  it 
afforded  the  first  example  of  the  formation,  by  artificial  methods 
from  inorganic  substances,  of  an  organic  compound  found  in 
the  animal  body  (see  p.  1). 

Urea  is  most  readily  obtained  from  urine. 

Experiment  47.  Evaporate  four  or  five  litres  fresh  urine  to  a  thin, 
syrupy  consistence.  After  cooling  add  ordinary  concentrated  nitric 
acid,  when  crystals  of  urea  nitrate  are  obtained.  Filter,  wash,  and 
recrystallize  from  moderately  concentrated  nitric  acid.  When  the 
crystals  of  urea  nitrate  are  white,  dissolve  again  in  water,  and  add 
finely-powdered  barium  carbonate.  The  nitric  acid  forms  barium 
nitrate,  and  the  urea  is  left  in  free  condition.  Evaporate  to  dryness, 
and  from  the  residue  extract  the  urea  with  strong  alcohol. 

Experiment  48.  Make  potassium  cyanate  as  directed  in  Experi- 
ments 24,  p.  82,  and  26,  p.  83.  To  the  cold  solution  of  the  cyanate  add 
a  solution  of  ammonium  sulphate  containing  as  much  of  the  salt  as 
there  was  used  of  potassium  ferrocyanide  in  the  preparation  of  the 
cyanate.  Evaporate  to  a  small  volume,  and  allow  to  cool.  Potassium 
sulphate  will  crystallize  out.  Filter  this  off,  and  evaporate  to  dryness. 
Extract  with  alcohol.  The  urea  will  crystallize  from  the  alcoholic 
solution  when  it  is  brought  to  the  proper  concentration.  Give  all  the 
reactions  involved  in  passing  from  potassium  ferrocyanide  to  urea. 
Compare  the  urea  made  artificially  with  that  made  from  urine. 

Urea  crystallizes  from  alcohol  in  large  quadratic  prisms, 
which  melt  at  132°. 

Experiment  49.  Determine  the  melting-points  of  both  the  natural 
and  artificial  specimens  of  urea. 

Urea  is  easily  soluble  in  water  and  alcohol.    Heated  with  water 


202         MIXED   COMPOUNDS    CONTAINING   NITROGEN. 

in  a  sealed  tube  to  100°,  it  breaks  up  into  carbon  dioxide 
and  ammonia  :  — 

CON2H4  +  H2O  =  CO2  -f  2  NH3. 

The  same  decomposition  of  the  urea  takes  place  spontaneously 
when  urine  is  allowed  to  stand.  Hence  the  odor  of  ammonia 
is  always  noticed  in  the  neighborhood  of  urinals  which  are  not 
kept  thoroughly  clean. 

Sodium  hypochlorite  or  hypobromite  decomposes  urea  into 
carbon  dioxide,  nitrogen,  and  water  :  — 

CON2H4  4-  3  NaOCl  =  NaaCO,  +  NaCl  +  N2  +  H2O  +  2  HC1. 


Experiment  5O.  To  a  solution  of  20&  sodium  hydroxide  in  100CC 
water  add  about  5CC  bromine,  and  shake  well.  Make  a  solution  of  urea 
in  water,  and  add  to  the  solution  of  the  hypobromite.  An  evolution 
of  gas  will  be  noticed,  showing  that  the  urea  is  decomposed. 

Nitrous  acid  acts  in  the  same  way  :  — 

CON2H4  +  2  HN02  =  CO2  +  N4  +  3  H2O. 

When  heated,  urea  loses  ammonia,  and  yields  first  biuret, 
and  finally  cyanuric  acid  (see  p.  84)  :  — 

2CO(NH2)2=  C2H5N302  +  NH3; 

Biuret. 

3  CO(NH2)2=  C3H303N3  +  3  NH3. 

Cyanuric  acid. 

Urea  unites  with  acids,  bases,  and  salts.  The  hydrogen  of 
the  amido  groups  may  be  replaced  by  acid  or  alcohol  radicals, 
giving  compounds  of  which  acetyl  urea,  CO<^'"2H3°,  and 


TI 

ethyl  urea,  CO  <  ™        »  are  examples. 

iN  -tl.j 

Among  the  compounds  with  acids,  the  following  may  be 
mentioned  :  urea  hydrochloride,  CH4N2O  .  HC1  ;  urea  nitrate, 
CH4N2O  .  HNO3  ;  and  urea  phosphate,  CH4N2O  .  H3PO4.  With 
metals  it  forms  such  compounds  as  that  with  mercuric  oxide, 
HgO.CH4N.2O  ;  with  silver,  CH2N2O  .  Ag2,  etc.  With  salts  it  forms 
such  compounds  as  HgCl2  .  CH4N2O,  HgO.CH4N2O.HNO3,  etc. 


PABABANIC    ACID.  203 

Substituted  ureas,  —  that  is,  those  derivatives  of  urea  which 
contain  hydrocarbon  residues  in  place  of  one  or  all  the  hydrogen 
atoms,  —  may  be  made  from  the  cyanates  of  substituted  ammo- 
nias. The  fundamental  reaction  is  the  spontaneous  transforma- 
tion of  ammonium  cyanate  into  urea  :  — 

CN.ONH4  =  CO(NH2)2. 

In  the  same  way,  cyanates  of  substituted  ammonias  are  trans- 
formed into  substituted  ureas  :  — 

CN  .ONH3  .C2H5     =  CO  < 


CN.ONH2(C2H5)2  =  CO  <     TTs52,  etc. 

JNH2 

The  urea  derivatives  which  contain  acid  radicals  are  made  by 
treating  urea  with  the  acid  chlorides  :  — 


CO<ATTT2  +  C2H3OC1  =  CO 

•N-0*  NH2 

Acetyl  urea. 

NOTE  FOR  STUDENT.  —  In  what  sense  is  acetyl  urea  analogous  to 
acetamide? 

There  are  several  derivatives  of  urea  and  radicals  of  bibasic 
acids,  as  oxalic  and  malonic  acids,  which  are  of  special  interest, 
as  they  are  closely  related  to  uric  acid  ;  and  their  formation  from 
this  acid  has  thrown  much  needed  light  upon  the  inner  nature  of 
the  acid. 

Parabanic  acid,  i  _  _  /    CO.NH  \ 

*      \  C3H2N,O3  =  1  >  CO  .  —Parabanic 

Oxalylurea,  V    CO.NH  / 

acid  is  formed  by  boiling  uric  acid  with  strong  nitric  acid  and 
other  oxidizing  agents,  and  by  treating  a  mixture  of  urea  and 
oxalic  acid  with  phosphorus  trichloride  :  — 

C2H2O4  4-  CO(NH2)2=  CSH2N2O3  +  2  H2O. 


204        MIXED   COMPOUNDS   CONTAINING  NITROGEN. 

It  acts  like  an  acid.  Its  salts  readily  pass  over  into  salts  of 
oxaluric  acid  (which  see)  .  Treated  with  alkalies  it  breaks  up 
into  urea  and  oxalic  acid.  As  will  be  seen,  parabanic  acid  is 

CO  .  NH2 
analogous  to  oxamide,    |  ,  the  residue  of  urea  acting  the 

CO  .  NH2 
part  of  the  two  amido  groups. 

/     CO.OH  \ 

Oxaluric  acid,  C3H4N2OA=  CO.HN.CO.NH2/,  bears  to 
parabanic  acid  the  same  relation  that  oxarnic  acid  bears  to 
oxamide.  It  occurs  in  the  form  of  the  ammonium  salt  in  small 
quantity  in  human  urine. 

Barbituric  acid,  malonyl  urea, 


aH4N203  +  2  H20(  =  CH2  <  SS'SS  >  CO  V  —  Barbituric 
\  L<(J.JNxl  f 

acid,  like  parabanic  acid,  is  a  product  obtained  from  uric  acid. 
It  has  been  made  artificially  by  treating  a  mixture  of  malonic 
acid  and  urea  with  phosphorus  oxichloride  :  — 


CH*<  COOT  +  C°  <          -  °H2  <  CO.  NH  >  C° 


Treated  with  an  alkali,  barbituric  acid  breaks  up  into  malonic 
acid  and  urea. 

The  relation  of  the  acid  to  malonic  acid  and  urea  is  the  same 
as  that  of  parabanic  acid  to  oxalic  acid  and  urea. 

Sulpho  urea,  CS(NH2)2.  —  This  substance  is  formed  by 
heating  ammonium  sulpho-cyanate,  the  reaction  which  takes 
place  being  analogous  to  that  by  which  urea  is  formed  from 
ammonium  cyanate  :  — 

CNSNH4  =  CS(NH2)2. 

A  number  of  derivatives  of  sulpho  urea  have  been  made. 
They  resemble  those  obtained  from  urea. 


XANTHINE.  205 

Uric  acid,  C5H4N4O3.  —  Uric  acid  occurs  in  human  urine, 
in  certain  urinary  calculi,  in  the  urine  of  carnivorous  animals, 
and  of  birds.  The  excrement  of  serpents  consists  almost 
entirely  of  ammonium  urate.  It  has  been  made  by  heating 
together  amido-acetic  acid  and  urea. 

Uric  acid  is  best  prepared  either  from  serpents'  excrement  or 
guano. 

It  forms  a  crystalline  powder,  which  is  almost  insoluble  in 
water.  It  is  a  monobasic  acid,  though  weak  compounds  with  the 
alkali  metals  may  be  made  which  contain  two  atoms  of  metal 
in  the  molecule. 

Uric  acid  has  been  the  subject  of  a  large  number  of  inter- 
esting investigations,  and  many  derivatives  have  been  obtained 
from  it.  It  would  only  tend  to  confusion  to  give  an  account  of 
many  of  these  derivatives  here.  Hence  only  a  few  of  the  trans- 
formations which  have  been  effected,  and  which  give  an  insight 
into  the  nature  of  the  acid,  will  be  mentioned. 

1.  By  heating  uric  acid,  ammonia,  hydrocyanic  acid  and  urea 
are  formed. 

2.  Heated  with  hydriodic  acid,  it  yields  carbon  dioxide,  ammo- 
nia, and  glycine  :  — 

C5H4N4O3  +  5  H2O  =  3  CO2  -f  3  NH3  +  C2H5NO2. 

3.  Oxidizing  agents  convert  uric  acid  either  into  allantoin, 
a  complicated  substance  of  the  formula  C4H6N4O3,  or  alloxan, 
C4H2N2O4,  which  is  closely  related  to  parabanic  acid,  or  oxalyl 
urea  (see  p.  203),  and  barbituric  acid,  or  malonyl  urea  (see 
p.  204). 

Xanthine,  C^H^NiC^,  is  found  in  some  rare  urinary  calculi 
and  in  several  animal  liquids.  It  is  formed  by  the  action  of 
nitrous  acid  on  guaniue,  C5H5N5O  :  — 

C5H5N50  +  HN02  =  C5H4N402  +  H2O  +  N2. 
This  reaction  shows  that  guaniue  is  an  amido  derivative,  and 


206         MIXED   COMPOUNDS    CONTAINING   NITROGEN. 

that  xanthine  is  the  corresponding  Irydroxyl  compound.  (Why 
does  this  follow?) 

Theobromine.  )  f 

Dimethyl-xanthine,  I  C™<M=  C5H2(CH3)2N4O2],    ,s    a 

substance  found  in  chocolate  prepared  from  the  seed  of  the 
cacao  tree.  It  has  been  made  by  treating  the  lead  compound 
of  xanthine  with  methyl  iodide. 

Caffeine,  theine,  trimethyl-xanthine, 

C8H10N4O2  +  H2O  [=C5H  (CH3)3N4O2  +  H2O],  is  the  active 
constituent  of  coffee  and  tea.  It  has  been  made  from  theo- 
bromine  by  the  introduction  of  a  third  methyl  group. 

Thus,  as  will  be  seen,  a  close  connection  is  established 
between  the  active  constituents  of  coffee,  tea,  and  chocolate  on 
the  one  hand,  and  xanthine  and  guanine  on  the  other. 

Guanine,C5H5N5O[-C5H3(NH,)N4OJ,  is  found  principally 
in  guano,  from  which  it  is  prepared.  Nitrous  acid  converts  it 
into  xanthine.  Oxidizing  agents  convert  it  into  guanidine, 
CN3H5  (seep.  199). 

RETROSPECT. 

Before  passing  on  to  the  next  division  of  our  subject,  it  will 
be  well  to  pause  and  consider  briefly  what  we  have  learned 
thus  far. 

In  the  first  place,  all  the  compounds  which  we  have  considered 
may  be  regarded  as  derived  from  the  marsh-gas  hydrocarbons 
or  paraffins. 

By  replacing  the  hydrogen  atoms  of  these  hydrocarbons  with 
chlorine,  bromine,  or  iodine,  we  get  (1)  the  substitution-products 
of  the  hydrocarbons. 

By  introducing  hydroxyl  into  a  Irydrocarbon  in  place  of 
hydrogen,  we  get  the  bodies  called  (2)  alcohols,  of  which 


RETROSPECT.  207 

there  are  three  classes :  (a)  the  primary,  (6)  the  secondary, 
and  (c)  the  tertiary  alcohols. 

By  oxidizing  primarj'  alcohols  we  get  (3)  aldehydes. 

By  oxidizing  secondary  alcohols  we  get  (4)  ketones. 

By  oxidizing  alcohols,  aldehydes,  and  ketones,  we  get  (5) 
acids. 

Acids  and  alcohols  act  upon  each  other,  forming  (6)  ethereal 
salts,  and  alcohols  can  be  converted  into  (7)  ethers. 

Corresponding  to  the  oxygen  derivatives,  we  met  with  com- 
pounds containing  sulphur,  as  (8)  the  sulphur  alcohols,  or 
mercaptans;  (9)  the  sulphur  ethers;  and  (10)  the  sulphonic 
acids. 

Next,  we  found  compounds  containing  nitrogen.  Under  this 
head  we  considered  cyanogen,  and  the  allied  compounds  hydro- 
cyanic, cyanic,  and  sulpho-cyanic  acids.  Allied  to  these  we 
found  (11)  the  cyanides,  and  (12)  the  isocyanides;  (13)  the 
cyanates,  and  (14)  the  isocyanates;  (15)  the  sulpho-cyanates, 
and  (16)  the  iso-sulpho-cyanates  or  mustard  oils. 

Finall}*,  we  found  (17)  compounds  containing  metals  in  combi- 
nation with  radicals. 

Representatives  of  these  various  classes  of  compounds  were 
considered,  and  the  relations  between  them  pointed  out. 

We  found  poly -acid  alcohols  and  poly -basic  acids. 

Under  the  head  of  mixed  compounds  were  found  compounds 
which  belong  at  the  same  time  to  two  or  more  of  the  funda- 
mental classes.,  as  the  hydroxy -acids,  the  carbo-hydrates,  and 
the  amido-acids.  A  consideration  of  the  amido-acids  and 
the  acid  amides  brought  us  naturally  to  the  consideration  of 
urea  and  its  derivatives,  and  of  uric  acid  and  its  derivatives. 

We  turn  now  to  a  new  class  of  compounds,  known  as  unsatu- 
rated  compounds. 


CHAPTER   XIII. 

UNSATURATBD    CARBON    COMPOUNDS.  -  DIS- 
TINCTION   BETWEEN   SATURATED   AND 
UNSATURATED    COMPOUNDS. 

ALL  the  compounds  thus  far  considered  are  generally  called 
saturated  compounds.  This  is  certainly  an  appropriate  name 
as  far  as  the  hydrocarbons  themselves  and  some  of  the  classes 
of  their  derivatives  are  concerned.  The  expression  "saturated" 
is  intended  to  signify  that  the  compounds  have  no  power  to  unite 
directly  with  other  compounds  or  elements.  Thus  marsh  gas 
cannot  be  made  to  unite  directly  with  anything.  Bromine,  for 
example,  must  first  displace  hydrogen  before  it  can  enter  into 
combination  with  the  compound 

CH4  -f-  Br2  =  CH3Br  +  HBr. 

The  compound  is  saturated. 

On  the  other  hand,  a  compound  which  can  take  up  elements 
or  other  compounds  directly  is  called  unsaturated.  Thus,  phos- 
phorus trichloride  is  unsaturated,  for  it  has  the  power  to  take 
up  two  chlorine  atoms  thus  :  — 

PC13  +  C12  =  PCI*. 

Ammonia  is  unsaturated,  for  it  can  take  up  other  elements  :  — 
NH3  +  HC1  =  NH4C1. 


TJNSATURATED   CARBON   COMPOUNDS.  209 

The  condition  of  unsaturation  is  met  with  among  carbon 
compounds  in  several  forms  :  — 

First.  The  aldehydes  act  like  unsaturated  compounds,  as 
shown  in  their  power  to  take  up  ammonia,  hydrocyanic  acid, 
and  other  substances. 

Second.  The  ke tones  also  act  like  unsaturated  compounds, 
though  their  power  in  this  way  is  less  marked  than  that  of  the 
aldehydes. 

Third.  The  substituted  ammonias  are  unsaturated,  in  the 
same  sense  in  which  ammonia  itself  is  unsaturated. 

Fourth.  The  cyanides  take  up  hydrogen  directly,  and  are 
therefore  unsaturated  also. 

In  the  substituted  ammonias,  and  probably  in  the  cyanides, 
the  unsaturation  is  due  to  the  same  cause  as  that  in  ammonia. 
In  them  the  nitrogen  is  trivalent.  In  contact  with  certain 
substances  it  becomes  quinquivalent,  and  saturates  itself. 

In  the  aldehydes  and  ketones,  carbon  is  in  combination  with 
oxygen  in  the  carbonyl  condition.  When  they  unite  with 
hydrogen  and  some  compounds,  such  as  hydrocyanic  acid,  the 
relation  between  the  carbon  and  oxygen  is  probably  changed, 
the  latter  being  in  the  hydroxyl  condition.  The  changes  are 
usually  represented  b}T  formulas  such  as  the  following  :  — 

CH3 .  C  v^  TT  ~f~  H2  =  CH3  .C  ^  TT    i 


CH3  CH 

I  I 

C  =  O  +  HCN  =  C  C 

I  I 

CH,  CH 


In  the  carbonyl  group  the  oxygen  is  represented  as  held  by 
two  bonds  by  the  carbon  atom,  while  in  the  hydroxyl  condition 
it  is  represented  as  held  by  one  bond.  The  signs  may  be  used 
if  care  is  taken  to  avoid  a  too  literal  interpretation  of  them. 
There  are  undoubtedly  two  relations  which  carbon  and  oxygen 


210       UNSATURATED  CARBON  COMPOUNDS. 

bear  to  each  other  in  carbon  compounds.  These  relations  may 
be  called  the  Jiydroxyl  relation,  represented  by  the  sign  C— O— , 
and  the  carbonyl  relation,  represented  by  the  sign  C  =  O. 

Fifth.  There  is  a  fifth  kind  of  nnsaturation,  dependent  upon 
differences  in  the  relations  between  carbon  atoms,  and  it  is  this 
kind  which  is  ordinarily  meant  when  unsaturated  carbon  com- 
pounds are  spoken  of. 

The  kind  of  relation  between  the  carbon  atoms  in  all  the 
saturated  hydrocarbons  is,  so  far  as  we  know,  the  same  as  that 
which  exists  between  the  two  carbon  atoms  of  ethane,  and 

H  H 

which   is    represented    by   the    formula    H  — C— C  — H.       This 

I      I 
H    H 

formula  signifies  simply  that  the  two  carbon  atoms  are  held 
together  by  the  forces  which  in  marsh  gas  enabled  each  carbon 
atom  to  hold  one  hydrogen  atom.  Abstracting  one  hydrogen 
atom  from  marsh  gas,  union  is  effected  between  the  carbon 
atoms.  What  would  result  if  two  hydrogen  atoms  were  to  be 
abstracted,  and  union  between  the  carbons  then  effected? 
Theoretically  we  should  get  a  compound  made  up  of  two  groups 
CH2,  thus  CH2.CH2,  and  presumably  the  relation  between  the 
carbon  atoms  in  this  compound  would  be  different  from  the 
relation  between  the  carbon  atoms  in  ethane.  Without  push- 
ing these  speculations  farther,  it  may  be  said  that  there  is  a 
well-known  hydrocarbon  which  differs  markedly  from  ethane, 
having  the  formula  C2H4,  and  showing  the  property  of  unsatu- 
ration  very  clearly.  This  is  olejiant  gas  or  ethylene.  It  is  the 
first  of  a  homologous  series  of  hydrocarbons,  only  a  very  few  of 
which,  however,  are  well  known.  These  hydrocarbons  yield 
derivatives  like  the  paraffins  ;  though  of  these,  as  well  as  of  the 
hydrocarbons,  very  few  are  known  as  compared  with  the  number 
of  the  paraffin  derivatives.  Only  a  few  of  them  are  of  much 
importance. 


ETHYLENE.  211 

ETHYLENE  AND    ITS  DERIVATIVES. 
HYDROCARBONS,  CnH2n. 

The  principal  hydrocarbons  of  this  series  are  included  in  the 
subjoined  table :  — 

Ethylene .  C2H4. 

Propylene C3HC. 

Butylene C4H8. 

Amylene C5H10. 

Hexylene ;.     .     .  C6H12. 

Heptylene C7H14. 

The  members  are  homologous  with  ethylene.  They  bear  to 
the  paraffins  a  very  simple  relation,  each  one  containing  two 
atoms  of  hydrogen  less  than  the  paraffin  with  the  same  number 
of  carbon  atoms. 

Ethylene,  olefiant  gas,  02H4(=  CH2.CH2).  —  This  gas  is 
formed  when  many  organic  substances  are  subjected  to  dry 
distillation.  The  two  principal  reactions  which  yield  it  are  :  — 

(1)  The  action  of  an  alcoholic  solution  of  potassium  hydrox- 
ide on  ethyl  chloride,  bromide,  or  iodide  :  — 

C2H5Br  +  KOH  =  C2H4  +  KBr  +  H2O. 

This  is  the  most  important  reaction  for  the  preparation  of  the 
unsaturated  compounds  of  the  ethyleue  series.  It  is  applicable 
not  only  to  the  hydrocarbons  but  to  substances  belonging  to 
other  classes.  By  means  of  it  we  have  it  in  our  power  to  pass 
from  any  saturated  compound  to  the  corresponding  unsaturated 
compound  of  the  ethylene  series.  Thus  we  pass  from  ethane, 
C2H6,  to  ethylene,  C2H4,  by  first  introducing  bromine,  and  then 
abstracting  hydrobromic  acid  from  the  mono-bromine  substitu- 
tion-product. Similarly,  by  treatment  with  alcoholic  potash  of 


212       UNSATUKATED  CARBON  COMPOUNDS. 

the  mono-bromine  substitution-products  of  other  compounds, 
the  corresponding  unsaturated  compounds  may  be  made. 

(2)  The  action  of  sulphuric  acid  and  other  dehydration 
agents  upon  alcohol :  — 

C2H5.OH  =  C2H4  +  H2O. 

Experiment  51.  In  a  flask  of  21  to  3'  capacity  put  a  mixture  of 
258  alcohol  and  1508  ordinary  concentrated  sulphuric  acid.  Heat  to 
160°  to  170°,  and  add  gradually  through  a  funnel  tube  about  500CC  of  a 
mixture  of  1  part  of  alcohol  arid  2  parts  of  concentrated  sulphuric  acid. 
Pass  the  gas  through  three  wash  bottles  containing,  in  order,  sulphuric 
acid,  caustic  soda,  and  sulphuric  acid.  Then  pass  it  into  bromine 
contained  in  a  cylinder,  provided  with  a  cork  with  two  holes.  If  the 
cylinder  has  a  diameter  of  about  5cm,  let  the  layer  of  bromine  be  about 
5cm  to  7cm  thick.  Upon  it  pour  a  somewhat  thicker  layer  of  water. 
Place  the  cylinder  in  a  vessel  containing  cold  water.  Pass  the  gas 
into  the  bromine  until  it  is  completely  decolorized. 

Eth}Tlene  is  a  colorless  gas  which  may  be  condensed  to  a 
liquid.  It  burns  with  a  luminous  flame.  With  oxygen  it  forms 
an  explosive  mixture.  Its  most  characteristic  property  is  its 
power  to  unite  directly  with  other  substances,  particularly  with 
the  halogens  and  their  hydrogen  acids.  Thus  it  unites  with 
chlorine  and  bromine,  and  with  hydriodic  and  hydrobromic 
acids :  — 

C2H4  -f-  C12     —  C2H4C12  i 

C2H4  +  Br2     =  C2H4Br2 ; 

C2H4  +  HBr  =  C,H5Br ; 

C2H4  +  HI     =  C2H5T. 

The  products  formed  with  chlorine  and  bromine  are  called 
rthylene  chloride  and  ethylene  bromide.  They  have  been 
mentioned  under  the  head  of  halogen  derivatives  of  the  paraf- 
fins. They  are  isomeric  with  ethylidene  chloride  and  ethylidene 
bromide,  which  are  formed  by  substitution  of  two  hydrogens 
of  ethane  with  chlorine  or  bromine. 


ETHYL  EN  E.  213 

NOTE.  —  The  addition  of  bromine  to  ethylene  is  illustrated  by  the 
experiment  last  performed,  in  which  ethylene  bromide  is  formed.  To 
purify  the  product,  put  a  little  dilute  caustic  soda  in  the  cylinder,  and 
shake,  liemove  the  upper  layer  of  water,  and  repeat  the  washing  with 
dilute  ca,ustic  soda.  Then  wash  with  water  two  or  three  times,  each 
time  removing  the  water  with  the  aid  of  the  pipette  described  on  p.  31. 
Finally,  put  the  oil  in  a  flask,  add  a  few  pieces  of  granulated  calcium 
chloride,  and  allow  to  stand.  Pour  off  into  a  dry  distilliug-bulb,  and 
distil,  noting  the  temperature. 

A  question  which  we  may  fairly  ask  concerning  the  structure 
of  ethylene  is  this :  Does  it  consist  of  two  groups  CH2,  or  of 
a  methyl  group,  CH3,  and  CH  ?  Is  it  to  be  represented  by  the 
formula  CH2.CH2  or  CH3.CH?  Perhaps  *  the  clearest  answer 
to  this  question  is  found  in  the  fact  that  the  chloride  formed  by 
addition  of  chlorine  to  ethylene,  and  that  formed  by  replacing 
the  oxygen  in  aldehyde  by  chlorine,  are  not  identical.  All 
evidence  is  in  favor  of  the  view  that  aldehyde  is  correctly 

represented   by   the    formula   CH3.Cjj.      Hence,    as   has    been 

pointed  out,  the  chloride  obtained  from  it  must  be  represented 
thus,  CH3.CHC12.  Hence,  further,  it  appears  highly  probable 
that  the  isomeric  chloride  obtained  from  ethylene  must  be 
represented  thus,  CH2CI.CH2C1.  Now,  as  this  substance  is 
formed  by  direct  addition  of  chlorine  to  ethylene,  ethylene  has 

CH2  CH3 

the  formula  I      ,  and  not  I 

CH2  CH 

As  regards  the  relation  between  the  two  carbon  atoms  of 
ethylene  we  know  nothing,  save  that  it  is  probably  different 
from  that  which  exists  between  the  carbon  atoms  of  ethane. 

CH2 
It  is  usually  represented  by  the  sign  =  ;  thus,  ||     .     We  must 

CH, 

necessarily  leave  the  question  open  as  to  the  relation  between 
the  carbon  atoms  in  ethylene.  If  the  above  sign  is  used,  it 
should  serve  mainly  as  an  indication  of  the  kind  of  unsaturation 
met  with  in  ethylene,  the  compound  in  whose  formula  it  in 
written  having  the  power  to  take  up  two  atoms  of  bromine,  a 
molecule  of  hydrobro.nic  acid,  etc. 


214  TINS  A  TITRATED    CARBON   COMPOUNDS. 

The  homologues  of  ethylene  bear  the  same  relation  to  it  that 
the  homologues  of  ethane  bear  to  this  hydrocarbon.     Propylene 

CH.CH3 
is  methyl-ethylene,   I  ,  just  as  propane  is  methyl-ethane, 

CH2.CH3  CH2  CH.CH3  C(CH3)2 

I  .      Butylene  is  dimethyl-ethylene,    I  ,  or   I 

CH3  CH.C2H5  CH.CH,          CH2 

or  ethyl-ethylene,    I  .      That  is  to  say,  in  other  words, 

CH2 

in  the  hydrocarbons  of  the  ethylene  series  the  ethylene  condi- 
tion between  carbon  atoms  occurs  only  once. 

The  higher  members  of  the  series  need  not  be  considered. 


ALCOHOLS,  CnH2nO. 

These  alcohols  bear  to  the  ethylene  hydrocarbons  the  same 
relation  that  the  alcohols  of  the  methyl  alcohol  series  bear  to 
the  paraffins.  Only  one  is  well  known.  This  is  the  second 
member  corresponding  to  propylene. 

Allyl  alcohol,  C3HGO(=  CH2.CH.CH2OH).  — This  alcohol 
is  formed  in  several  ways  from  glycerin. 

1.  By  introducing  two  chlorine  atoms  into  glycerin  in  the 
place  of  two  hydroxyls,  thus  getting  dichlorhydrin,  C3H5C12 .  OH  : 

CH2OH  CH2C1 

I  Hn  I 

CHOH  +  "^  =  CHC1  +  2  H2O ; 

I  I 

CH2OH  CH2OH 

and  treating  the  dichlorhydrin  with  sodium,  which  extracts  the 
chlorine :  — 

CHoCl  CH2 

I  I 

CHC1     +  2  Na  =  CH         +2  NaCl. 

I  I 

CH2OH  CH2OH 


ALLYL   MUSTARD    OIL.  215 

2.  By  treating  glycerin  with  the  iodide  of  phosphorus.     This 
gives  allyl  iodide,  C3H5I.     By  treating  the  iodide  with  silver 
hydroxide  it  is  converted  into  the  alcohol. 

3.  Most  readily  by  treating  glycerin  with  oxalic  acid,  as  in 
the  preparation  of  formic  acid.     The  mixture  is  heated  to  220° 
to  230°,  when  allyl  alcohol  passes  over. 

It  is  manufactured  in  this  way  on  the  large  scale  for  the  pur- 
pose of  making  artificial  oil  of  mustard.  The  reactions  involved 
are  quite  complicated. 

Allyl  alcohol  is  a  liquid  boiling  between  99°  and  100°.  It 
has  a  penetrating  odor. 

Nascent  hydrogen,  from  zinc  and  hydrochloric  acid,  converts 
it  partially  into  propyl  alcohol :  — 

C3H5.OH  +  H2  =  C3H7.OH. 

The  relation  between  allyl  alcohol  and  propyl  alcohol  is  the 
same  as  that  between  ethylene  and  ethane. 

Allyl  alcohol,  like  ethylene,  unites  directly  with  bromine, 
Irydrobromic  acid,  etc.,  the  products  being  substitution-products 
of  propyl  alcohol :  — 

C3H5.OH  +  HBr  =  C3H6Br.OH, 

Monobrom-propyl  alcohol. 

C3H5.OH  +  2Br  =  C3H5Br2.OH. 

Dibrom-propyl  alcohol. 

Allyl  compounds.  —  Among  the  derivatives  of  allyl  alco- 
hol which  are  of  special  interest  is  allyl  sulphide,  (C3H5)2S, 
which  is  the  chief  constituent  of  the  oil  of  garlic.  It  may  be 
made  artificially  by  treating  allyl  iodide  with  potassium  sul- 
phide :  — 

2  C3H5I  +  K2S  =  (C3H5)2S  +  2  KI. 

It  is  an  oily  liquid  of  a  disagreeable  odor. 

Allyl  mustard  oil,  SON. C3H5.  —  Under  the  head  of 
Sulpho-cyanates  mention  was  made  of  a  series  of  isomeric 
bodies  called  isosulpho-cyanates  or  mustard  oils.  The  sulpho- 


216       UNSATURATED  CABBON  COMPOUNDS. 

cyauates    of   the    alcohol   radicals    are   made    from  potassium 

sulpho-cyanate.       Thus,    methyl    sulpho-cyanate    is  made    by 

mixing    together    potassium    methyl-sulphate    and  potassium 
sulpho-cyanate,  and  distilling  :  — 


2  =  K2S04  +  NCSCH3. 
KO     J 

The  mustard  oils,  on  the  other  hand,  are  made  by  a  compli- 
cated reaction  from  carbon  bisulphide  and  substituted  ammonias. 
The  conduct  of  the  sulpho-cyanates  led  us  to  the  conclusion 
that  they  must  be  represented  by  the  formula  NC  —  SB,  while 
that  of  the  isosulpho-cyanates  or  mustard  oils  led  to  the  for- 
mula SC—  NB,  as  representing  their  structure.  Allyl  mustard 
oil  is  the  chief  representative  of  the.  class  of  bodies  known 
as  mustard  oils.  It  occurs  as  a  glucoside  (see  p.  178)  in 
mustard  seed.  From  the  glucoside  it  is  formed  by  fermenta- 
tion. It  is  formed  by  treating  allyl  iodide  with  potassium 
sulpho-cyanate.  We  would  naturally  expect  this  reaction  to 
yield  allyl  sulpho-cyanate,  but  the  compound  actually  obtained 
does  not  conduct  itself  like  the  sulpho-cyanates. 

Allyl  mustard  oil  is  a  liquid,  boiling  at  150.7°,  and  having  a 
penetrating  odor. 

With  zinc  and  hydrochloric  acid  it  is  converted  into  allyl- 
amine,  NH2.C3H5,  hydrogen  sulphide  and  carbon  dioxide.  This 
reaction  indicates  that  in  allyl  mustard  oil  the  radical  allyl  is  in 
combination  with  the  nitrogen  and  not  with  the  sul^nur. 

NOTE  FOR  STUDENT.  —  What  change  do  the  mustard  oils  in  general 
undergo  when  treated  with  nascent  hydrogen?  What  change  do  the 
sulpho-cyanates  undergo  under  the  same  circumstances? 

Acrolein,  acrylic  aldehyde,  C3H,O(=  C2H3.COH).—  Acro- 

lei'n  may  be  made  by  careful  oxidation  of  allyl  alcohol.  It  is 
formed  by  the  dry  distillation  of  glycerin  which  breaks  up  into 
water  and  acrolei'n  :  — 

C3H803  =  C3H40  +  2  H20. 


ACIDS,  CnH2n_2O2-  217 

It  is,  hence,  formed  also  by  heating  the  ordinary  fats,  the 
peculiar  penetrating  odor  noticed  when  fatty  substances  are 
heated  to  a  sufficiently  high  temperature  being  due  to  the  forma- 
tion of  acrole'in.  It  is  prepared  best  by  heating  glycerin  with 
acid  potassium  sulphate. 

Experiment  52.  In  a  test-tube  mix  anhydrous  glycerin  (I  part) 
and  acid  potassium  sulphate  (2  parts) ,  and  heat  the  mixture.  Pass 
the  vapors  through  a  bent  tube  into  water  contained  in  another  test- 
tube.  Notice  the  odor.  Try  the  effect  on  a  dilute  solution  of  nitrate 
of  silver.  What  is  the  meaning  of  this  reaction? 

Acrolei'n  is  a  volatile  liquid  which  boils  at  52.4°.  It  has  an 
extremely  penetrating  odor,  and  its  vapor  acts  violently  upon 
the  eyes,  causing  the  secretion  of  tears. 

Acrolei'n  takes  up  oxygen  from  the  air,  and  is  converted  into 
the  corresponding  acid,  acrylic  acid,  C3H4O2  (which  see). 

It  takes  up  hydrogen,  and  is  thus  converted  into  allyl  alcohol. 

It  takes  up  hydrochloric  acid,  and  is  converted  into  /3-chlor- 
propionic  aldehyde  :  — 

C2H3.COH  +  HC1  =  CH2C1.CH2.COH. 

/3-chlor-propionic  aldehyde. 

The  first  two  reactions  are  characteristic  of  aldehydes  in 
general ;  the  last  one  is  characteristic  of  unsaturated  compounds 
belonging  to  the  ethylene  group.  Acrolei'n,  like  ordinary  alde- 
hyde, forms  polymeric  modifications,  which  can  easily  be  recon- 
verted into  acrolei'n. 

It  unites  with  ammonia  forming  acrolem-ammonia,  and  with 
other  substances  in  much  the  same  way  as  ordinary  aldehyde 
does. 

ACIDS,  CnH2n_2O2. 

Running  parallel  to  the  ethylene  series  of  hydrocarbons,  and 
bearing  the  same  relation  to  it  that  the  fatty  acid  series  bears 
to  the  paraffins,  is  a  series  of  acids  of  which  the  first  member 
is  acrylic  acid,  C3H4O?.  Several  members  of  the  series  are 


218       UNSATUKATED  CARBON  COMPOUNDS. 

known.     The  principal  members  are  named  in  the  subjoined 
table :  — 

ACRYLIC  ACID   SERIES. 
ACIDS,  CnH2n_2O2. 

Acrylic        acid C3H4O2. 

Crotonic        " C4H6O2. 

Angelic          " C5H8O2. 

Hydrosorbic"       ......  C6H10O2. 

Teracrylic     " CyH^Oa. 

Cimic  " C15H28O2. 

Hypogseic     " C16H30O2. 

Oleic  " C18H34O2. 

Erucic  " 


Of  most  of  the  higher  members  of  the  series  several  isomeric 
modifications  are  known.  Only  a  few  of  these  acids  will  be 
considered  here. 

Acrylic  acid,  O3H4O2(=  CH2.CH.CO,H).  —  This  acid  has 
already  been  mentioned  in  connection  with  hydracrylic  acid, 
which,  when  heated,  breaks  up  into  acrylic  acid  and  water :  — 

CH2.OH.CH2.CO2H,=  CH2.CH.CO2H  +  H2O. 

Hydracrylic  acid.  Acrylic  acid. 

NOTE  FOR  STUDENT.  —  This  reaction  is  analogous  to  that  which 
takes  place  when  ordinary  alcohol  is  converted  into  ethylene.  In  what 
does  the  analogy  consist?  What  acid  is  isomeric  with  hydracrylic 
acid?  How  does  it  conduct  itself  when  heated?  Compare  the  trans- 
formation of  hydracrylic  acid  into  acrylic  acid  with  that  of  malic  into 
malei'c  and  f  umaric  acids,  and  with  that  of  citric  into  aconitic  acid. 

Acrylic  acid  may  be  made  by  careful  oxidation  of  acrolei'n 
with  silver  oxide.  The  relations  between  propylene,  C3H6) 


OLEIC   ACID.  219 

allyl  alcohol,  C3H5.OH,  acrolei'n,  C2H3.COH,  and  acrylic  acid, 
C2H3.CO2H,  are  the  same  as  those  between  any  hydrocarbon  of 
the  paraffin  series,  and  the  corresponding  primary  alcohol, 
aldehyde,  and  acid. 

Acrylic  acid  may  be  made  further  by  treating  /?-iodo-propi- 
onic  acid  with  alcoholic  potash  :  — 

CHJ  .CH2  .CO2H  =  CH2  .CH  .CO2H  -f  HI. 

NOTE  FOR  STUDENT.  —  Compare  this  reaction  with  that  by  which 
ethylene  is  made  from  ethyl  bromide. 

Acrylic  acid  is  a  liquid  having  a  pungent  odor.  iu  boils  at 
140°,  and  solidifies  at  a  low  temperature. 

Nascent  hydrogen  converts  it  into  propionic  acid.  Hydri- 
odic  acid  unites  directly  with  it,  forming  /3-iodo-propionic  acid. 

NOTE  FOR  STUDENT.  —  What  are  the  analogous  reactions  with  allyl 
alcohol  and  acrolei'n? 

Many  derivatives  of  acrylic  acid  have  been  studied,  but  they 
need  not  be  taken  up  here. 

Crotonic  acid,  C4H6O2.  —  Crotonic  acid  is  made  from  allyl 
cyanide,  the  reactions  involved  being  represented  by  the 
following  equations :  — 

C3H5I  +  KCN         =  C3H5.CN  +  KI ; 

Allyl  iodide.  Allyl  cyanide. 

C3H5.CN  +  2H20  =  C3H5C02H  +  NH3. 

Crotonic  acid. 

It  may  be  made  also  by  distilling  /?-hydroxy-butyric  acid, 
CH3.CH(OH).CH2.CO2H,  when  a  reaction  takes  place  similar 
to  that  involved  in  the  preparation  of  acrylic  from  hydracylic 
acid.  Further,  it  may  be  made  by  treating  a-brom-butyric  acid 
with  alcoholic  potash. 

Oleic  acid,  C18H34O2.  —  This  acid  was  spoken  of  in  con- 
nection with  the  fats,  it  being  one  of  the  three  acids  found 


220  UNSATURATED   CARBON   COMPOUNDS. 

most  frequently  in  combination  with  glycerin.  Olein,  or 
glyceryl  tri-oleate,  is  the  liquid  fat,  and  is  the  chief  constituent 
of  the  fatty  oils,  such  as  olive  oil,  whale  oil,  etc.  It  is  con- 
tained also  in  almost  all  ordinary  fats.  In  the  preparation  of 
stearic  acid  for  the  manufacture  of  candles,  the  olem  is  pressed 
out  of  the  fats.  To  prepare  the  acid,  olem  is  saponified,  and 
the  soap  then  decomposed  with  hydrochloric  acid. 

NOTE  FOR  STUDENT.  —  Give  the  equations  representing  tlie  reac- 
tions involved  in  passing  from  olein,  or  glyceryl  tri-oleate,  to  olei'c  acid. 

Oleic  ttcid  is  a  crystallized  substance  which  melts  at  a  low 
temperature  (14°).  It  unites  with  bromine,  forming  bibrom- 
stearic  acid.  Hydriodic  acid  converts  it  into  stearic  acid  :  — 


^     TT     f~\         |       TT       ,,_._,_, 

Oleic  acid.  Stearic  acid. 

POLYBASIO   ACIDS   OF   THE    ETHYLENE    GROUP. 

There  are  a  few  bibasic  acids  which  bear  to  the  ethylene 
hydrocarbons  the  same  relations  that  the  members  of  the  oxalic 
acid  series  bear  to  the  paraffins.  They  may  be  regarded  as 
derived  from  the  hydrocarbons  by  the  introduction  of  two 
carboxyl  groups.. 

Acids,  C2H2(CO2H)2.  — There  are  two  acids  of  this  formula, 
both  of  which  have  been  mentioned.  They  are  fumaric  and 
maleic  acids ,  which  are  formed  b}'  the  distillation  of  malic  acid. 

NOTE  FOR  STUDENT.  —  What  is  the  reaction? 

Fumaric  acid  may  also  be  made  by  treating  brom-succinic 

CHBr.C02H 

acid,  I  ,  with  alcoholic  potash. 

CH2.C02H 

NOTE  FOR  STUDENT.  — What  is  the  reaction? 

Both  fumaric  and  maleic  acids  are  converted  into  succinic 


ACETYLENE   AND   ITS   DERIVATIVES.  221 

acid   by  nascent   hydrogen,    and   into   brom-succinic   acid    by 

hydrobromic  acid.     The  character  of   the  isomerism  of   these 

two  acids  is  not  understood.     Their  eas}7  transformation  into 

succinic  acid  and  brom-succinic  acid  shows  that  the  formula 

CH  .CO2H 

I  applies  to  both  of  them. 

CH.CO2H 

Acids,  C5H3O4.  —  There  are  three  acids  of  this  formula,  all 
of  which  are  obtained,  either  directly  or  indirectly,  from  citric 
acid.  They  are  known  as  itaconic,  citraconic,  and  mesaconic 
acids.  They  bear  the  same  relation  to  pyrotartaric  acid, 

PO  TT 

C3H6<      2   ,  thatfumaric  and  malei'c  acids  bear  to  succinic  acid. 

OvJoli 

All   are   converted   into   pyrotartaric  acid   by  treatment  with 
nascent  hydrogen. 


Aconitic  acid,  [CeHeCU-  C3H3(CO2H),)].  —  Aconitic  acid  is 
the  only  tri-basic  acid  of  this  group  that  need  be  mentioned. 
As  has  been  stated,  it  is  formed  when  citric  acid  is  heated  to 
175°.  It  is  found  in  nature  in  aconite  root,  and  in  the  sap  of 
sugar-cane  and  of  the  beet. 

Nascent  hydrogen  converts  it  into  tri-carballylic  acid, 
C3H5(C02H)3. 

ACETYLENE  AND  ITS  DERIVATIVES. 

The  principal  reactions  by  means  of  which  we  are  enabled  to 
pass  from  a  hydrocarbon  of  the  paraffin  series  to  the  corre- 
sponding hydrocarbon  of  the  ethylene  series  consist  in  intro- 
ducing a  halogen  into  the  paraffin,  and  then  treating  the 
mono-halogen  substitution-product  with  alcoholic  potash  :  -.  — 

C2H5Br  =  C2H4  +  HBr. 

The  effect  of  these  two  reactions  is  the  abstraction  of  two 
hydrogen  atoms  from  the  paraffin.  The  following  questions 
therefore  suggest  themselves  :  — 

Suppose  a  dibrom  substitution-product  of  a  paraffin  be  heated 


222       UNSATURATED  CARBON  COMPOUNDS. 

with  alcoholic  potash ;  will  the  effect  be  that  represented  by 
the  equation 

C2H4Br2  =  C2H2  +  2  HBr? 

And,  further,  suppose  a  mono-substitution  product  of  an 
ethylene  hydrocarbon  be  treated  with  alcoholic  potash ;  will  the 
effect  be  that  represented  by  the  equation 

C2H3Br  =  C2H2  +  HBr? 

If  so,  it  is  plain  that  we  have  it  in  our  power  to  make  a  new 
series  of  hydrocarbons,  the  members  of  which  shall  bear  to  the 
ethylene  hydrocarbons  the  same  relation  that  the  latter  bear  to 
the  paraffins.  The  general  formula  of  this  series  would  be 
CnH2n_2,  that  of  the  ethylene  series  being  CnH2n,  and  that  of  the 
paraffin  series,  CnH2n+2. 

A  few  members  of  the  hydrocarbon  series,  CnH2n_2,  are 
known,  though  only  one  is  well  known,  and  only  this  one  need 
be  considered. 

Acetylene,  C2H2.  —  Acetylene  is  formed  by  direct  combina- 
tion of  hydrogen  and  carbon  when  a  current  of  hydrogen  is 
passed  between  carbon  poles,  which  are  incandescent  in  conse- 
quence of  the  passage  of  an  electric  current ;  when  alcohol, 
ether,  and  other  organic  substances  are  passed  through  a  tube 
heated  to  redness ;  when  coal  gas  and  some  other  substances 
are  burned  in  an  insufficient  supply  of  air  ;  and  when  ethylene 
bromide  is  treated  with  alcoholic  potash  :  — 

C2H4Br2  =  C2H2  4-  2  HBr. 

It  may  be  prepared  most  conveniently  by  the  incomplete  com- 
bustion of  coal  gas. 

Experiment  53.  —  Light  a  Bunsen  burner  at  the  base,  and  turn  it 
down  so  that  the  flame  is  small.  The  condition  is  the  same  as  that 
observed  when  a  burner  "strikes  back."  The  odor  noticed,  which  is 
familiar  to  every  one  who  has  worked  in  a  chemical  laboratory,  is 
that  of  acetylene,  which  is  mixed  with  the  products  given  off  from 


ACETYLENE. 


223 


the  burner.  To  collect  the  gas,  arrange  an  apparatus  as  shown  in 
Fig.  13.  Place  the  glass  funnel  over  the  burner,  from  which  acety- 
lene is  given  off.  In  B  put  a  strong  solution  of  ammoniacal  cuprous 
chloride  prepared  as  follows :  Make  a  saturated  solution  of  1  part 
common  salt  and  2]  parts  crystallized  copper  sulphate.  Saturate  with 
sulphur  dioxide.  Filter,  and  wash  with  acetic  acid.  Dissolve  the 
white  cuprous  chloride  in  ammonia. 


Fig.  13. 

Connect  the  apparatus  at  O  with  some  kind  of  aspirator  (suction- 
pump,  a  gasometer  filled  with  water,  etc.),  and  draw  the  gases  slowly 
through  the  solution.  The  acetylene  will  be  absorbed  by  the  copper 
solution,  and  a  precipitate  formed  (see  Exp.  54). 

Acetylene  is  a  gas  of  an  unpleasant  odor.  It  burns  with  a 
luminous,  sooty  flame. 

When  heated  to  a  sufficiently  high  temperature,  it  is  con- 
verted into  the  polymeric  substances,  benzene,  C6He,  and  sty- 
rene,  C8H8.  It  unites  with  hydrogen  to  form  ethylene  and 


224  TJNSATURATED    CARBON    COMPOUNDS. 

ethane.      It  unites  with   nitrogen,   under  the  influence  of  the 
sparks  from  an  induction  coil,  forming  hydrocyanic  acid :  — 

C2H2  +  2-N  =  2HCN. 

Acetylene  forms  some  curious  compounds  with  metals  and 
metallic  oxides.  Among  them  may  be  mentioned  the  copper 
compound  obtained  in  Exp.  53.  This  has  the  composition, 
C2H2.Cu2O,  being  a  compound  of  acetylene  and  cuprous  oxide. 
It  is  a  reddish-brown  substance  which  is  insoluble  in  water. 
When  dry,  it  explodes  violently  at  120°.  Hydrochloric  acid 
decomposes  it,  acetylene  being  evolved. 

Experiment  54.  Filter  off  the  precipitate  obtained  in  Exp.  53, 
and  wash  it  until  the  wash-water  runs  through  colorless.  Bring  the 
precipitate,  together  with  a  little  water,  into  a  flask  furnished  with  a 
funnel-tube  and  a  delivery-tube.  Slowly  add  concentrated  hydro- 
chloric acid,  and  notice  the  evolution  of  gas.  Collect  some  of  it 
in  a  small  cylinder  over  water,  and  burn  it. 

Acetylene  unites  with  bromine,  forming  the  compound 
C2H2Br4,  tetra-brom-ethane.  It  unites  with  hydrobromic  and 
hydriodic  acids,  forming  substitution-products  of  the  satu- 
rated hydrocarbons :  — 

C2H2  +  2  HI  =  C2H  J2. 

Most  of  the  higher  members  of  the  acetylene  series  of  hydro- 
carbons bear  to  acetylene  the  same  relation  that  the  higher  mem- 
bers of  the  ethylene  series  bear  to  ethylene.  The  first  one  is 

C.CH3 

Allylene  or  methyl-acetylene  \  ; 

CH 

the  second  is 

C.C2H5 

Ethyl-acetylene I  , 

CH 

C.CH3 

or         Dimethyl-acetylene I 

C.CH8 


PROPARGYL  ALCOHOL.  225 

It  should  be  noticed  in  this  connection  that  there  is  a  hydro- 
carbon of  the  formula  C4H6,  which,  strictly  speaking,  is  not 
a  homologue  of  acetylene,  though  it  is  very  closely  allied  to 

CH  =  CH2 
dimethyl-acetylene.     It  has  the  formula  I 

CH  =  CH2 

The  homologues  of  acetylene  may  be  divided  into  two 
classes  :  — 

1  .  Those  which  are  obtained  from  acetylene  by  the  replace- 
ment of  one  or  both  the  hydrogen  atoms  by  saturated  radicals, 
such  as  methyl,  etlryl,  etc.  These  may  be  called  the  true  homo- 
logues.  They  all  retain  the  condition  peculiar  to  acetylene. 

2.  Those  in  which  the  ethylene  condition  occurs  twice,  as  in 
the  hydrocarbons  of  the  formulas 

CH  =  CH2  C(CH3)2 

I  II  etc. 

CH=CH2  C 


These  may  be  called  diethylene  derivatives. 

We  know  nothing  regarding  the  relation  between  the  carbon 
atoms  in  acetylene.     It  is  commonly  represented  by  three  lines 

CH 
(  =  )  ,  or  three  clots  (  \  )  .    Thus,  acetylene  is  written  I  ;  |     or  CH  •  CH. 

\_yj~JL 

Like  the  sign  for  the  ethylene  condition,  it  should  not  be  inter- 
preted too  literally.  It  is  best  to  regard  it  as  the  sign  of  a 
condition  best  illustrated  in  acetylene,  and  which  may  therefore 
be  called  the  acetylene  condition.  We  recognize  this  condition  in 
a  compound  by  the  power  of  the  compound  to  take  up  four  atoms 
of  a  halogen,  or  two  molecules  of  hydrobromic  acid  and  similar 
acids;  though,  as  we  have  seen,  these  reactions  are  not  distinc- 
tive for  the  acetylene  condition,  for  the  reason  that  the  diethy- 
lene compounds  have  the  same  power. 


Propargyl  alcohol,  CUE^O.  —  This  alcohol  is  mentioned 
merely  as  an  example  of  alcohols  which  are  derived  from  the 
acetylene  hydrocarbons.  It  is  the  hydroxyl  derivative  of 


226  UNSATURATED    CARBON    COMPOUNDS. 

allylene,  or  methyl-acetylene.  It  is  made  by  treating  brom- 
allyl  alcohol,  C3H4Br.OH,  with  alcoholic  potash:  — 

CsH4Br.OH  =  C3H3.OH  +  HBr. 

ACIDS,  CnH2n_4O2. 

These  acids  are  the  carboxyl  derivatives  of  the  acetylene 
hydrocarbons,  and  hence  differ  from  the  members  of  the 
acrylic  acid  series  by  two  atoms  of  h}*drogen  each,  and  from 
the  members  of  the  fatty  acid  series  by  four  atoms  of  hydro- 
gen each. 

/OH          \ 
Propiolic  acid,  C3H2O2(  =   |  1.  —  The  bromine  and 

v      C .  CO2H/ 

chlorine  substitution-products  of  this  acid  are  more  easily  made 
and  are  better  known  than  propiolic  acid  itself.  Chlor-propio- 
lic  acid  is  obtained  by  treating  diehlor-acrylic  acid  with  baryta 
water :  — 

C2HC12.CO2H  =  C2C1.CO2H  +  HC1. 

/    C.CH3    \ 

Tetrolic    acid,   C4H4O2[  =  I  J,  is  obtained  by  treating 

N    C.CO2H/ 

/?-chlor-crotonic  acid  with  caustic  potash  :  — 

CC1.CH3        C.CH3 
|  =   |  +  HCL 

CH.CO2H      C.CO2H 

Sorbic  acid,  CGH«O2(=  C5H7.CO2H).  — This  acid  occurs  in 
the  unripe  berries  of  the  mountain  ash.  It  takes  up  hydrogen 
and  yields  hydrosorbic  acid,  a  member  of  the  acrylic  acid  series 
(see  table,  p.  218).  It  also  takes  up  bromine,  the  final  product 
of  the  action  being  an  acid  of  the  formula  C5H7Br4.CO2H.  With 
hydrobromic  acid  it  forms  dibrom-caproic  acid  :  — 

C5H7.CO2H  +  2  HBr  =  C5H9Br2.CO2H. 

Dibrom-caproic  acid. 


DIPKOPAIIGYL.  227 

Leinoleic  acid,  Ci6H28O2(=  C1:H27.CO2H). — This  acid  occurs 
in  the  form  of  an  ethereal  salt  of  glycerin  in  linseed  oil.  It  may 
be  obtained  from  linseed  oil  by  saponification.  It  is  an  oily 
liquid,  one  of  the  most  marked  properties  of  which  is  its  power 
to  take  up  ox}rgen  from  the  air,  being  thus  transformed  into  a 
solid  substance.  Linseed  oil  itself  has  this  property  of  harden- 
ing or  drying.  It  is  the  principal  substance  belonging  to  the 
class  of  drying  oils.  The  oil  is  used  extensively  as  a  constituent 
of  varnishes  and  of  oil  paints. 


Valylene,  C3H6.  —  We  have  thus  far  had  to  deal  with  three 
series  of  hydrocarbons  of  the  general  formulas  CnH2n  +  2,  CnH2n, 
and  CnH2n_2.  We  naturally  inquire  whether  there  is  a  series  of 
the  general  formula  CnH2n_4.  A  few  members  of  the  series  have 
been  prepared  by  abstracting  hydrogen  from  certain  of  the  acety- 
lene hydrocarbons  by  the  action  of  alcoholic  potash  on  the  bro- 
mine derivatives.  Thus,  valylene,  C5H6,  has  been  made  by 
treating  valerylene  bromide,  C5H8Br2,  with  alcoholic  potash :  — 

C5H8Br2  =  C5H6  +  2  HBr. 

It  is  a  liquid.  Its  most  characteristic  property  is  its  power  to 
unite  with  bromine  to  form  the  saturated  compound  C5H6Br6. 

Dipropargyl,  C6H6.  —  Dipropargyl  is  obtained  from  the 
compound  dibrom-diallyl,  C6H8Br2,  by  boiling  with  alcoholic 
caustic  potash :  — 

C6H8Br2  =  C6H6  +  2  HBr. 

It  unites  very  readily  with  bromine,  forming,  as  the  final 
product  of  the  action,  the  compound  C6H6Br8,  which  is  an 
octo-bromine  substitution-product  of  hexane,  C6H14. 


The  unsaturated  hydrocarbons  and  their  derivatives  thus  far 
considered  are  obtained  by  simple  reactions  from  the  saturated 


228        UNSATURATED  CARBON  COMPOUNDS. 

compounds,  and  they  all  have  the  power  to  take  up  readily 
bromine,  hydrobromic  acid,  etc.,  and  thus  to  pass  back  to  the 
saturated  condition.  Whatever  the  real  nature  of  the  relation 
between  the  carbon  atoms  in  all  these  unsaturated  hydrocarbons 
may  be,  it  certainly  is  easily  changed  to  the  condition  which 
exists  in  the  saturated  compounds.  There  are  several  hydro- 
carbons, however,  which  are  unsaturated  but  which  are  not 
easily  converted  into  derivatives  of  the  saturated  hydrocar- 
bons. Although  under  some  circumstances  they  with  diffi- 
culty unite  directly  with  the  halogens,  they  do  not  take  up 
enough  to  convert  them  into  derivatives  of  the  paraffins ;  and 
the  products  which  are  formed  are  unstable,  easily  giving  up 
the  halogen  atoms  with  which  the}*  united.  The  simplest 
hydrocarbon  of  this  new  kind  is  the  well-known  benzene, 
which  is  isomeric  with  dipropargyl.  Before  proceeding  to 
the  consideration  of  benzene  and  its  derivatives,  it  will  be 
well  to  inquire  whether  the  abstraction  of  l^drogeu  by  the 
reaction  chiefly  used  can  be  pushed  further  than  it  has  thus 
far  been  pushed.  Can  we,  in  other  words,  by  means  of  this 
reaction  get  hydrocarbons  of  the  formula  CnH2n_8  which  have 
the  power  to  unite  directly  with  ten  atoms  of  bromine?  Such 
hydrocarbons  have  not  been  prepared.  Hydrocarbons  of  the 
formula  CnH2n_8  are  known ;  but  they  are  not  made  from  the 
paraffins  lay  abstracting  hydrogen,  and  they  are  not  converted 
into  substitution-products  of  the  paraffins  by  the  addition  of 
halogens  and  halogen  acids.  The  compounds  which  have 
been  considered  fall  under  five  general  heads,  according  to  the 
formulas  of  the  hydrocarbons.  These  heads  are,  — 

1.  Hydrocarbons,  CnH2n  +  2,  the  paraffins  and  their  derivatives. 

2.  Hydrocarbons,  CnH2n,       or  olefins  and  their  derivatives. 

3.  Hydrocarbons,  CnH2n_2,    or  the   acetylene   hydrocarbons   and 

their  derivatives. 

4.  Hydrocarbons,  CnH2n_4,    and  their  derivatives. 

5.  Hydrocarbons,  CnH^.e,   and  their  derivatives. 


GENERAL   CONSIDERATIONS.  229 

This  classification,  while  strictly  correct,  is  misleading,  inas- 
much as  it  conveys  no  idea  in  regard  to  the-  relative  importance 
of  the  compounds  of  the  different  classes.  As  we  have  seen, 
the  only  compounds  whose  treatment  required  much  time  are 
those  of  the  first  class.  These  compounds  stand  out  promi- 
nently, and  are  distinguished  by  the  frequenc}7  of  their  occur- 
rence and  their  great  number.  The  compounds  of  the  second 
class  are  much  less  numerously  represented,  and  but  a  small 
number  of  them  are  familiar  substances.  While  a  few  sub- 
stances belonging  to  the  third  class  are  known,  our  knowledge 
in  regard  to  the  class  is  much  more  limited  than  even  that 
of  the  second  class.  Finally,  as  regards  the  fourth  and  fifth 
classes,  the  few  representatives  of  them  that  are  known  are  at 
present  scientific  curiosities.  Thus,  after  we  leave  the  paraffin 
derivatives,  our  knowledge  dwindles  away  very  rapidly  when 
we  pass  to  the  following  classes,  until  it  ends  with  a  single 
compound  in  the  fifth  class. 

We  pass  now  to  the  consideration  of  a  new  group,  the  impor- 
tance and  number  of  whose  members  entitle  it  to  be  placed  side 
by  side  with  the  group  of  paraffin  derivatives. 


CHAPTER  XIV. 

THE    BENZENE    SERIES    OF    HYDROCARBONS.  - 
AROMATIC    COMPOUNDS. 

THE  fundamental  substance  of  this  group  is  benzene,  C6H6, 
which  bears  to  the  group  the  same  relation  that  marsh  gas 
bears  to  the  group  of  paraffin  derivatives.  Benzene,  together 
with  some  of  its  homologues,  is  a  product  of  the  distillation  of 
bituminous  coal,  and  is,  therefore,  contained  in  coal  tar.  As 
coal  tar  is  the  raw  material  from  which  all  benzene  derivatives 
are  obtained,  it  will  be  well  briefly  to  consider  the  conditions 
of  its  formation  and  the  method  of  obtaining  pure  hydrocarbons 
from  it. 

Coal  tar  is  a  thick,  black,  tarry  liquid,  which  is  obtained  in 
the  manufacture  of  illuminating  gas  from  bituminous  coal. 
The  coal  is  heated  in  retorts,  and  all  the  products  passed 
through  a  series  of  tubes  called  condensers.  These  are  kept 
cool,  and  in  them  the  liquid  and  volatile  solid  products  are  con- 
densed, forming  together  the  coal  tar.  It  is  an  extremely  com- 
plex mixture,  from  which  a  great  many  substances  have  been 
obtained.  Among  those  most  readily  obtained  from  it  are  the 
hydrocarbons  of  the  benzene  series,  as  well  as  the  hydrocarbons 
naphthalene  and  anthracene,  both  of  which  are  important  sub- 
stances. 

When  the  tar  is  heated,  of  course  the  most  volatile  liquids 
pass  over  first.  These  are  collected  in  vessels  containing  water. 
The  first  portions  of  the  distillate  float  on  water,  and  constitute 
what  is  called  the  light  oil.  After  a  time  hydrocarbons  and 
other  substances  of  greater  specific  gravity  than  the  light  oil 


BENZENE   SERIES.  231 

pass  over.  These  portions  sink  under  water,  and  constitute  the 
heavy  oil. 

The  light  oil  is  treated  with  caustic  soda,  which  removes 
phenol  (carbolic  acid)  and  similar  substances,  and  with 
sulphuric  acid,  which  removes  certain  basic  compounds.  The 
residue  is  then  subjected  to  fractional  distillation,  by  which 
means  the  first  two  members  of  the  series  can  be  obtained  in 
very  nearly  pure  condition.  As  these  hydrocarbons  form  the 
basis  of  a  number  of  important  industries,  they  are  separated 
from  coal  tar  on  the  large  scale. 

The  principal  members  of  the  series  are  named  in  the  table 
below. 

HYDROCARBONS,  CnH2n_6. 

BENZENE  SERIES. 
Benzene     .........     C6H6. 

Toluene     .........     C7H8. 

Xylene  ..........     C8H10. 

Mesitylene        ) 

\       ...... 

Pseudocumene  ) 

Durene  ) 

~  f     ......... 

Cymene  j 

Hexa-methyl  benzene   ..... 


Benzene,  C6H6.  —  Benzene  is  prepared,  as  above  described, 
from  the  light  oil  obtained  from  coal  tar.  It  is  also  prepared 
by  heating  benzoic  acid  with  lime,  when  the  acid  breaks  up 
into  carbon  dioxide  and  benzene  :  — 

C7H602  =  C6H6  -f  C02. 

NOTE  FOR  STUDENT.  —  What  is  the  analogous  method  for  the 
preparation  of  marsh  gas? 

Benzene  has  been  made  further  by  simply  heating  acetylene  : 

O 


232  BENZENE   SERIES    OF   HYDROCARBONS. 

To  purify  the  hydrocarbon  obtained  by  fractional  distillation 
from  light  oil,  it  is  cooled  down  to  a  low  temperature,  and  that 
which  does  not  solidify  is  poured  off.  The  crystals  are  pressed 
in  the  cold  between  layers  of  bibulous  paper,  and  are  then  very 
nearly  pure  benzene.  This  may  be  further  purified  by  treat- 
ment with  sulphuric  acid,  which  removes  a  small  quantity  of  a 
substance  containing  sulphur,  and  known  as  thiophene.  Per- 
fectly pure  benzene  is  obtained  by  distilling  pure  ben  zoic  acid 
with  lime. 

Experiment  55.  Mix  intimately  50s  benzole  acid  and  I00»  quick- 
lime, and  distil  from  a  flask  connected  with  a  condenser.  See  that  the 
materials  and  apparatus  are  dry.  Add  a  little  calcium  chloride  to  the 
distillate;  and,  after  it  has  stood  for  an  hour  or  two,  redistil  it  from 
an  appropriate  sized  distilling-bulb,  noting  the  temperature  at  which  it 
boils.  Put  the  redistilled  hydrocarbon  in  a  test-tube,  and  surround  it 
with  a  freezing  mixture. 

Experiment  56. —  In  most  places  where  there  are  gas-works  it  will 
not  be  difficult  to  get  a  quantity  of  light  oil.  The  separation  of  some 
of  this  into  benzene  and  toluene,  and  the  purification  of  the  two  hydro- 
carbons, is  the  best  possible  introduction  to  a  study  of  the  aromatic 
compounds.  The  benzene  and  toluene  thus  obtained  may  be  used  in  the 
preparation  of  a  number  of  typical  derivatives  according  to  methods 
which  will  be  described.  In  f  ractioning  the  light  oil,,  it  will  be  observed, 
that  there  is  a  tendency  to  an  accumulation  of  the  distillates  in  the 
parts  boiling  near  80°  (the  boiling-point  of  benzene)  and  110°  (the  boil- 
ing-point of  toluene).  The  final  purification  of  the  benzene  should  be 
effected  by  freezing  and  pressing,  as  described  above.  The  toluene 
should  be  distilled  until  by  redistillation  its  boiling-point  is  not  changed. 

Benzene  is  a  colorless  liquid  which  boils  at  80.5°.  It  has  a 
peculiar,  pleasant  odor.  Several  of  the  homologues  of  benzene 
have  a  similar  odor.  Hence  the  name  aromatic  compounds  was 
given  to  them  originally,  and  it  is  still  in  general  use.  Benzene 
is  lighter  than  water,  its  specific  gravity  being  0.899  at  0°.  It 
burns  with  a  bright,  luminous  flame. 

Experiment  57.  —  Pour  a  layer  of  benzene  on  water  in  a  small 
evaporating-dish.  Set  fire  to  it, 


BENZENE.  233 

At  0°  benzene  solidifies,  forming  rhombic  prisms.  It  is  an 
excellent  solvent  for  oily  and  resinous  substances.1 

Chemical  conduct  of  benzene,  and  hypothesis  regarding  its 
structure.  In  the  light  of  the  knowledge  we  have  already 
gained  in  studying  hydrocarbons  which  contain  a  smaller  pro- 
portion of  hydrogen  than  the  paraffins  do,  we  would  naturally 
expect  to  find  that  benzene  can  easily  be  converted  into  a 
derivative  of  hexane.  We  would  naturally  expect  to  find 
that  it  unites  with  bromine,  just  as  dipropargyl  does,  to 
form  an  octo-brom-hexane  thus, — 

C6H6  +  Br8  =  C6H6Br8 ; 
with  hydrobromic  acid  to  form  tetra-brom-hexane  thus,  — 

C6H6  +  4HBr  =  C6H10Br4; 
and  probably  with  hydrogen  to  form  hexane,  — 
C6H6  -f-  8  H  =  C6H14. 

But  none  of  these  reactions  takes  place.  Hydrobromic  acid, 
which  acts  so  readily  on  all  the  unsaturated  compounds  hitherto 
considered,  does  not  act  at  all  upon  benzene.  Bromine  acts 
readily  enough,  but  the  action  which  usually  takes  place  is 
like  that  which  takes  place  with  the  saturated  paraffins.  It  is 
substitution,  and  not  addition.  Thus,  bromine  forms  mono- 
brom-benzene,  C6H5Br,  under  ordinary  circumstances.  If, 
however,  the  action  takes  place  in  the  direct  sunlight,  a  prod- 
uct is  formed  which  has  the  formula  C6H6Br6,  known  as 
benzene  hexabromide,  and  to  this  no  more  bromine  can  be 
added.  Further,  benzene  hexabromide  is  an  unstable  com- 
pound, —  much  less  stable  than  benzene.  When  heated,  it 
breaks  up,  partly  according  to  the  equation 

C6H6Br6  =  C6H3Br3  +  3  HBr, 

1  Benzene,  the  chemical  individual  of  the  definite  formula  CGHfi,  must  not  be  con- 
founded with  "  benzine,"  the  commercial  substance  obtained  in  the  refining  of  petro- 
leum (see  p.  110). 


234  BENZENE   SERIES    OF    HYDROCARBONS. 

the  chief  product  being  a  substitution-product  of  benzene, — 
tri-brom-benzeue,  C6H3Br3. 

Treated  with  hydriodic  acid,  benzene  takes  up  six  atoms  of 
hydrogen,  and  yields  a  hydrocarbon,  C6H12,  which,  however,  does 
not  act  like  a  member  of  the  ethylene  series,  as  it  appears  to 
have  no  power  to  take  up  bromine,  etc.,  and  shows  a  marked 
tendency  to  pass  back  into  benzene,  particularly  under  the  influ- 
ence of  oxidizing  agents. 

The  facts  mentioned  show  clearly  that  benzene  differs  in  some 
way  fundamentally  from  all  the  hydrocarbons  which  have  been 
considered.  But  these  facts  are  not  sufficient  to  enable  us  to 
form  a  hypothesis  in  regard  to  its  structure.  On  studying  the 
many  substitution-products  of  benzene,  however,  we  soon  become 
acquainted  with  facts  of  a  different  order  and  of  the  highest  im- 
portance. 

It  will  be  remembered  that  our  theory  in  regard  to  the  rela- 
tions of  the  paraffins  to  each  other  is  based  upon  the  fact,  that 
only  one  mono-substitution  product  of  marsh  gas  can  be  obtained 
with  any  given  substituting  agent.  There  is  but  one  chlor- 
methane,  but  one  brom-methane,  etc.  This  fact  leads  us  to 
believe  that  each  hydrogen  atom  of  marsh  gas  bears  the  same 
relation  to  the  carbon  atom,  or  that  marsh  gas  is  a  S3'mmetrical 
compound.  A  similar  conclusion  has  been  reached  in  regard  to 
benzene  ;  and  it  is  based  upon  a  most  exhaustive  study  of  the 
substitution-products.  Notwithstanding  almost  innumerable 
efforts  to  prepare  isomeric  mono-substitution  products  of  ben- 
zene, no  such  isomeric  substances  have  been  prepared.  There 
is  but  one  mono-brom-benzene,  but  one  mono-chlor-benzene, 
etc.,  etc.  Further,  mono-brom-benzene  has  been  prepared  by 
replacing  the  six  hydrogen  atoms  of  benzene  successively  by 
bromine ;  and  the  product  has  been  found  to  be  the  same,  no 
matter  which  hydrogen  is  replaced.  As  this  fact  is  of  funda- 
mental importance,  it  will  be  well  to  consider  how  it  is  possible 
to  replace  the  six  hydrogens  successively,  and  to  know  that  in 
each  case  a  different  hydrogen  atom  is  replaced.  While  it  would 


BENZENE.  235 

lead  us  too  far  to  consider  this  subject  in  detail,  the  principle 
made  use  of  can  be  made  clear  in  a  few  words  :  — 

We  have  a  compound,  the  formula  of  which  is  C6H6.     Write 

123456 

it  thus,  C6HHHHHH,  numbering  the  hydrogen  symbols  to  facil- 

i 
itate  reference  to  them.     The  problem  is  to  replace,  say  H,  by 

2 

bromine ;    in  a  second  case,  to  replace  H  by  bromine ;    in  a 

third,  H,  etc  ;  and  to  compare  the  six  mono-brom-berizenes  thus 
obtained.  Suppose  we  treat  benzene  with  bromine.  We  get 
a  mono-brom-benzene,  and  we  know  that  one  of  the  hydrogen 
atoms  is  replaced  by  bromine,  but  of  course  we  cannot  tell 
which  one.  We  may  assume  that  it  is  any  one  of  the  six 
represented  in  the  above  formula.  For  the  sake  of  the  argu- 

1  23456 

ment,  call  it  H.  Our  compound  is  therefore  C6BrHHHHH. 
Now  treat  this  compound  with  something  else  which  has  the 
power  to  replace  the  hydrogen,  say  nitric  acid.  A  second 
hydrogen  atom  is  replaced  by  the  nitro  group  NO2.  Again, 
we  do  not  know  which  one  of  the  hydrogen  atoms  is  replaced 
in  this  operation,  but  we  do  know  that  it  is  a  different  one 
from  that  which  was  replaced  by  the  bromine  in  the  first 

operation.      Call   it   H.      We    have,   therefore,  the   compound 

3456 

C6Br(NO2)HHHH.  By  treating  this  compound  with  nascent 
hydrogen,  two  reactions  take  place,  the  chief  one  for  our 

present  purpose   being   the   replacement   of   the    bromine    by 

i 
hydrogen.      In   other  words,    H   is   put   back   into   the   com- 

1  3456 

pound  again,  and  we  have  C6H(NO2)HHHH.  By  means 
of  two  reactions  which  will  be  considered  a  little  later  it  is 
a  simple  matter  to  replace  the  nitro  group  by  bromine.  This 

1  3    4    ,5    6 

done,  we  have  the  compound  C6HBrHHHH,  or  a  mono-brom- 
benzene,  in  which  the  bromine  certainly  replaces  a  different 
nydrogen  atom  from  that  replaced  by  direct  substitution.  The 
two  products  are,  however,  identical.  The  above  explanation 
will  serve  to  make  the  principle  clear  which  is  involved  in  the 


236  BENZENE   SEBIES    OF   HYDttOCAKBONS. 

study  of  the  relations  which  the  hydrogen  atoms  contained  in 
benzene  bear  to  the  molecule.  The  principle  has  been  applied 
successfully  to  all  the  hydrogen  atoms,  and,  as  already  stated, 
the  result  is  the  proof  that  all  these  hydrogen  atoms  bear  the 
same  relation  to  the  molecule. 

Thus  far  we  have  formed  no  conception  in  regard  to  the  rela- 
tions existing  between  the  constituents  of  benzene.  Can  we, 
on  the  basis  of  the  facts  above  stated,  form  any  satisfactor}* 
conception  in  regard  to  these  relations  ?  How  can  we  imagine 
six  carbon  atoms  and  six  hydrogen  atoms  arranged  so  that  all 
the  latter  shall  bear  the  same  relation  to  the  molecule?  The 
simplest  conception  is  that  each  carbon  is  in  combination  with 
one  hydrogen,  and  that  the  six  carbon  atoms  are  arranged  in 
the  form  of  a  ring,  and  not,  as  in  the  paraffins,  in  the  form  of 
an  open  chain,  or  a  chain  with  branches.  Using  our  ordinary 
method  of  representation,  this  conception  is  symbolized  in  the 
formula 


HCV  /CH 


or,  as  the  curved  lines  have  no  special  significance,  the  expres- 
sion becomes  jj 

UC/    ^Ctt 

I        I 

HCX     /CH 

xcx 

H 

This  symbol,  then,  is  the  expression  of  a  thought  which  is 
suggested  by   a  study   of  the   chemical   conduct  of  benzene. 


BENZENE.  237 

Before  we  can  accept  it  as  probable,  it  must  first  be  tested  by 
all  the  facts  known  to  us.  If  it  is  not  in  accordance  with  all  of 
them,  if  it  suggests  possibilities  which  are  not  realized,  then  it 
must  be  discarded,  and  we  must  form  some  other  conception  in 
regard  to  the  structure  of  benzene. 

In  the  first  place,  then,  does  it  account  for  the  addition 
products,  benzene  hexabromide,  hexa-hydro-benzene,  etc.  ?  The 
formula  represents  each  carbon  atom  as  trivalent,  and  we  would 
expect,  therefore,  that  each  one  could  take  up  an  additional 
univalent  atom,  forming,  in  the  case  of  bromine,  a  compound 
of  the  formula 


BrHC7    XCHBr 

I  i 

BrHC\     /CHBr 

xcr 

HBr 

in  which  each  carbon  atom  is  acting  as  a  quadrivalent  atom. 
Unless  the  ring  form  of  combination  between  the  carbon  atoms 
is  broken  up,  it  is  impossible  for  the  compound  to  take  up  more 
bromine.  Hence,  the  last  product  of  the  addition  of  bromine 
to  benzene  should  be  benzene  hexabromide  ;  and,  in  the  same 
way,  the  last  product  of  the  addition  of  hydrogen  should  be 
hexa-hydro-benzene,  as  it  is.  The  facts  and  the  hypothesis  are 
in  harmony. 

Again,  we  may  inquire  :  Of  how  many  isomeric  bi-substitu- 
tion  products  of  benzene  does  the  hypothesis  suggest  the  exist- 
ence? Numbering  the  hydrogens  in  the  formula,  we  have  :  — 


C 

XCH(2) 

(5)HCV  /CH(3) 

xcr 

H(4) 
The  hydrogens  (1)  and  (2),  (2)  and  (3),  (3)  and  (4),  (4)  and 


238       BENZENE  SERIES  OF  HYDROCARBONS. 

(5),  (5)  and  (6),  and  (6)  and  (1),  bear  the  same  relations  to 
each  other ;  and,  according  to  the  formula,  whether  we  replace 
(1)  and  (2),  or  (2)  and  (3),  or  (3)  and  (4),  or  any  other  of 
the  above-named  pairs,  the  product  ought  to  be  the  same.  We 
would  get  a  compound  of  which  the  following  is  the  general 
expression,  in  which  X  represents  any  substituting  atom  or 
group :  —  x 

ip 

HC/    XCX 

I  I 

HCX      /CH 

xcr 

H 

Formula  I. 

In  the  second  place,  the  hydrogens  (1)  and  (3),  (2)  and 
(4),  (3)  and  (5),  (4)  and  (6),  (5)  and  (1),  and  (6)  and  (2) 
bear  to  each  other  the  same  relation,  but  a  different  relation 
from  that  which  the  above  pairs  do.  Replacing  any  such  pair, 
we  would  have  a  second  compound,  which  is  represented  by 
the  general  formula 

X 

xCv 

HC/    XCH 

HCX     /CX 

xcr 

H 

Formula  II. 

Finally,  there  is  a  third  kind  of  relation,  which  is  that  between 
hydrogens  (1)  and  (4),  (2)  and  (5),  and  (3)  and  (6)  ;  and,  by 
replacing  such  a  pair,  we  should  get  a  compound  represented 
by  the  general  formula  ^. 

HCX^XCH 

I  I 

HCV     /CH 

xcr 
x 

Formula  III. 


BENZENE.  239 

The  hypothesis  suggests  no  other  possibilities.  We  see  thus 
that  the  hypothesis  indicates  the  existence  of  three,  and  only 
three,  classes  of  bi-substitution  products  of  benzene.  There 
ought  to  be  three,  and  only  three,  bi-chlor-benzenes  ;  three, 
and  only  three,  bi-brom-benzenes,  etc. 

The  di-substitution  products  have  been  studied  very  exhaust- 
ively for  the  purpose  of  determining  definite!}*  whether  the 
conclusion  above  reached  is  in  accordance  with  the  facts  ;  and 
it  may  be  said  at  once,  that  every  fact  thus  far  discovered  is  in 
harmony  -with  the  hypothesis.  Three  well-marked  classes  of 
isomeric  di-substitution  products  of  benzene  are  known,  and 
only  three  ;  and  many  representatives  of  the  three  classes  have 
bjen  studied  carefully.  There  are  many  other  facts  of  less 
importance  known  which  furnish  arguments  in  favor  of  the  ben- 
zene hypothesis  expressed  in  the  formula  above  discussed,  but 
this  is  not  the  place  to  consider  them.  Let  it  suffice,  for  the 
present,  to  recognize  that  the  hypothesis  is  in  accordance  with 
the  most  important  facts  known  to  us. 

There  is  one  point  which  has  not  been  touched  upon,  and 
that  is  the  relation  of  the  carbon  atoms  to  each  other.  In 
regard  to  this,  as  well  as  to  the  relation  between  the  carbon 
atoms  in  ethylene  and  acetylene,  we  know  nothing.  The 
formula  is  commonly  written  thus  :  — 


H 


\ 
XCH 


H 

which  indicates  that  the  carbon  atoms  are  joined  together 
alternately  by  simple  and  by  double  bonds.  This  formula, 
however,  expresses  something  about  which  we  know  nothing, 
and  concerning  which  it  is  difficult,  at  present,  to  form  any 
conception.  The  simple  formula 


240       BENZENE  SERIES  OF  HYDROCARBONS. 


H 

C 


HC.       /CH 

^V 
H 

leaves  the  question  as  to  the  relation  between  the  carbon  atoms 
entirely  open,  as  it  is  in  fact. 

The  benzene  hypothesis  has  thus  been  considered  pretty  fully 
for  the  reasons,  that  it  has  played  an  extremely  important  part 
in  the  study  of  the  benzene  derivatives,  that  its  use  serves 
greatly  to  simplify  the  study  of  these  derivatives,  and  that  in 
most  text-books,  whether  elementary  or  advanced,  the  hypothesis 
is  merely  stated,  while  the  student  is  left  to  find  out  for  himself 
its  meaning,  and  this  he  generally  fails  to  do.  We  may  now 
return  to  a  stud}7  of  the  facts  upon  which  the  hypothesis  is 
founded,  and  of  which  the  formula  is  the  symbolic  expression. 

Toluene,  C7H8(=  C6H5.CH3).  —  Toluene  was  known  before 
it  was  obtained  from  coal  tar,  as  it  is  formed  by  the  dry  distilla- 
tion of  Tolu  balsam,  whence  its  name.  Its  relation  to  benzene 
is  shown  by  its  synthesis  from  brom-benzene  and  methyl 
iodide  :  — 

C6H5Br  +  CH3I  +  Na2  =  C6H5.CH3  +  NaBr  +  Nal. 

NOTE  FOR  STUDENT.  —  Compare  this  reaction  with  that  used  in  the 
synthesis  of  ethane  from  methane,  of  propane  from  ethane  and 
methane,  etc. 

According  to  this  synthesis,  toluene  appears  as  methyl-benzene, 
or  benzene  in  which  one  hydrogen  is  replaced  by  methyl  ;  or  as 
plienyl-methane,  or  methane  in  which  one  'hydrogen  atom  is  re- 
placed by  the  radical  phenyl,  C6H5,  which  bears  the  same 
relation  to  benzene  that  methyl  bears  to  marsh  gas. 


XYLENES.  241 

Toluene  is  a  colorless  liquid  which  boils  at  110°;  has  the 
specific  gravity  0.8824  at  0° ;  and  has  a  pleasant  aromatic 
odor. 

It  is  very  susceptible  to  the  action  of  reagents  yielding  a  large 
number  of  substitution-products,  some  of  the  most  important 
of  which  will  be  considered  farther  on. 

But  one  toluene  or  methyl-benzene  has  ever  been  discovered. 

Towards  oxidizing  agents  its  conduct  is  peculiar  and  interest- 
ing. The  methyl  is  oxidized,  while  the  phenyl  remains  intact. 
The  product  is  a  well-known  acid,  benzoic  acid,  which,  as  we 
have  seen,  breaks  up  readily  into  carbon  dioxide  and  benzene. 
It  has  the  composition  C7H6O2,  and  is  the  carboxyl  derivative 
of  benzene,  C6H5.CO2H.  The  oxidation  of  toluene  is  repre- 
sented by  the  equation 

C6H5.CH3  +  30  =  C6H5.C02H  +  H2O. 

Xylenes,  C8H10[=  C6H4(CH3)2].  —  That  portion  of  light  oil 
which  boils  at  about  140°  was  originally  called  xylene.  It 
was  afterwards  found  that  this  coal-tar  xylene  consists  of 
three  isomeric  hydrocarbons.  As  the  boiling-points  of  these 
three  substances  lie  quite  near  together,  it  is  impossible  to 
separate  them  by  means  of  fractional  distillation.  By  treat- 
ment with  sulphuric  acid,  however,  they  may  be  separated, 
and  thus  obtained  in  pure  condition.  They  are  known  as 
ortlio -xylene,  meta-xylene,  and  para-xylene. 

Ortho-xylene  resembles  benzene  and  toluene  in  its  general 
properties,  but  boils  at  142°  to  143°. 

Meta-xylene  boils  at  139.8°. 

Para-xylene  boils  at  136°  to  137°. 

These  hydrocarbons  have  also  been  obtained  from  toluene  by 


242       BENZENE  SERIES  OF  HYDROCARBONS. 

means  of  the  reaction  made  use  of  for  the  purpose  of  converting 
benzene  into  toluene  :  — 

C6H4<  ™3  +  CH3I  +  2  Na  =  C6H4<  ^3  +NaBr  +  Nal. 
13r  ^H3 

This  shows  that  they  are  all  methyl-toluenes.  There  are 
three  mono-brom-toluenes,  known  as  ortho-,  meta-,  and  para- 
brom- toluene.  For  the  preparation  of  ortho-xylene,  ortho- 
brom-toluene  is  used ;  meta-brom-toluene  yields  meta-xylene, 
and  para-brom-toluene  yields  para-xylene. 

Ortho-  and  meta-xylene  have  also  been  obtained  from  certain 
acids,  which  bear  to  them  the  same  relation  that  benzoic  acid 
bears  to  benzene  :  — 

(CH3 

C6H3 1  CH8     =  C6H4(CH3)2  +  C02. 
IC02H 

The  reaction  by  which  meta-xylene  is  formed  from  mesitylenic 
acid  is  of  special  importance,  as  will  be  pointed  out. 

By  oxidation,  the  xylenes  undergo  changes  like  that  which  is 
illustrated  in  the  formation  of  benzoic  acid  from  toluene,  and 
which  consists  in  the  transformation  of  methyl  into  carboxyl. 

/-ITT 

The  first  change  gives  acids  of  the  formula  C6H4<       3      one 

CO2H 

corresponding  to  each  xylene.      By  further  oxidation,   these 
three  monobasic  acids  are  converted  into  bibasic  acids  of  the 

C^C\  T-T 

formula  C6H4<CQ2H-     Thus,  we  have  the  three  reactions,  all 
of  the  same  kind:  — 

(1)  C6H5 .  CH3        +  3  O  =  C6H5 .  CO2H     -f  H2O  ; 

(2)  C6H4  <  Jg     +30  =  C6H4  <  £gH  +  H2o  . 

and     (3)  C6H4  <  ^    +30  =  C6H4  <  ™       +  H2O. 


XYLENES.  243 

/"1TT 

The  three  monobasic  acids  of  the  formula  ^eH*<QQ3jj  are 

known  as  ortlw-toluic,  meta-toluic,  and  para-toluic  acids  re- 
spectively ;  and  the  three  bibasic  acids  obtained  from  them 
are  known  as  ortJio -phthalic,  meta-pJithalic,  and  para-pJitkallc 
acids.  Starting  thus  from  the  three  brom- toluenes,  we  get, 
first,  three  xylenes,  then  three  toluic  acids,  and  finally  three 
phthalic  acids.  In  each  case,  we  distinguish  between  the 
three  isomeric  compounds  b}*  the  prefixes  ortho,  meta,  and 
para.  In  a  similar  way,  all  di-substitution  products  of  ben- 
zene are  designated.  We  therefore  have  three  series  into 
which  all  di-substitution  products  of  benzene  can  be  arranged ; 
and  these  are  known  as  the  Ortho-series,  the  Meta-series,  and 
the  Para-series.  In  arranging  them  in  this  way,  we  may 
select  any  prominent  di-substitution  product,  and  call  it  an 
ortho  compound;  and  then  call  one  of  its  isomerides  a  meta 
compound,  and  the  other  a  para  compound.  Having  thus  a 
representative  of  each  of  the  three  classes,  the  remainder  of 
the  problem  consists  in  determining  for  each  di-substitution 
product,  by  means  of  appropriate  reactions,  into  which  one 
of  the  three  representatives  it  can  be  transformed.  If  from 
a  given  compound  we  get  the  representative  of  the  ortho 
series,  we  conclude  that  the  compound  belongs  to  the  ortho 
series  ;  if  we  get  the  representative  of  the  meta  series,  we 
conclude  that  the  compound  is  a  meta  compound ;  and  if  we 
get  the  representative  of  the  para  series,  we  conclude  that 
the  compound  is  a  para  compound.  As  representatives,  we 
may  select  either  the  three  xj'lenes  or  the  three  phthalic 
acids.  Now,  to  repeat,  any  di-substitution  product  of  ben- 
zene which  can  be  converted  into  ortho-xylene  or  into  ortho- 
phthalic  acid  is  regarded  as  an  ortho  compound,  etc. 

This  classification  of  the  di-substitution  products  of  benzene 
into  the  ortho,  meta,  and  para  series,  by  means  of  chemical 
transformations,  is  entirely  independent  of  any  hypothesis  re- 


244  BENZENE   SERIES    OF   HYDROCARBONS. 

garding  the  nature  of  benzene.  We  may  now  ask,  however, 
which  one  of  the  three  general  expressions  given  above  (see 
formulas  I.,  II.,  and  III.,  p.  238)  represents  the  relation  of  the 
groups  in  the  ortho  compounds,  which  one  the  relation  in  the 
meta  compounds,  and  which  one  the  relation  in  the  para  com- 
pounds. If  we  can  answer  these  questions  for  any  three 
isomeric  di-substitution  products,  the  answer  for  the  rest  will 
follow.  To  reduce  the  problem  to  simple  terms,  therefore, 
let  us  take  the  three  xylenes.  We  have  three  xylenes  and 
three  formulas  :  how  can  we  determine  which  particular  form- 
ula to  assign  to  each  xylene  ? 

As  may  be  imagined,  this  determination  is  by  no  means  a 
simple  matter ;  and  it  has  been  the  occasion  of  a  great  man}7 
investigations.  Theoretically,  the  simplest  method  available 
consists  in  carefully  studying  the  substitution-products  of  each 
xylene,  to  discover  how  many  varieties  of  mono-substitution 
products  can  be  obtained  from  each.  The  formulas  are  :  — 

CH3  CH3  CH3 

C  C  C 

(4)HCX    XC.CH3     (4)HCX    XCH(1)     (4)HCX    XCH(1) 

(3)HCX     /CH(1)    (3)HCX      /CCH3      (3)HC\     /CH(2) 
\c/  \c/  \c/ 

H  H  PTT 

(2)  (2) 

Formula  I.  Formula  II.  Formula  III. 

Each  of  the  four  unreplaced  benzene  hydrogens  of  the  xylene 
of  formula  III.  bears  the  same  relation  to  the  molecule.  It 
therefore  should  make  no  difference  which  one  is  replaced,  the 
product  ought  to  be  the  same.  This  should  not  be  true  of 
the  xylenes  represented  by  formulas  I.  and  II.  That  xylene, 
whose  structure  is  represented  by  formula  III.,  ought  therefore 
to  yield  but  one  kind  of  mono-substitution  product.  On  study- 
ing the  xylenes,  we  find  the  one  which  boils  at  136°  to  137°, 


ETHYL-BENZENE.  245 

called  para-xylene,  yields  but  one  kind  of  mono-substitution 
products ;  .  that  is,  we  carl  get  from  it  only  one  mono-brom- 
xylene ;  only  one  motfo-iitro-xylene,  etc.  We  therefore  con- 
clude that  para-xylene  is  represented  by  formula  III.  above ; 
and,  further,  that  formula  III.,  on  p.  238,  is  the  general  ex- 
pression for  all  para  compounds. 

Examining  formula  I.,  on  the  preceding  page,  in  the  same 
way,  we  see  that  H(l)  and  H(4)  bear  the  same  relation  to  the 
molecule  ;  and  that  H(3)  and  H(2)  also  bear  the  same  relation 
to  the  molecule,  though  different  from  that  of  H(l)  and  H(4). 
Two  chlor-xylenes  of  the  formulas 

CH3  CH3 

HC7    XCCH3  RC/    XC.CH3 

I  I  and          I  I 

HCX      /CC1  HC\     /CH 

xcx  xcr 

H  Cl 

ought  to  be  obtainable  from  the  xylene  of  formula  I. 

In  the  same  way  three  mono-substitution  products  might  be 
obtainable  from  the  xylene  of  formula  II.  The  method,  the 
principle  of  which  is  thus  indicated  briefly,  while  theoretically 
simple  enough,  is  very  difficult  in  its  application,  except  in  the 
case  of  the  para  compounds.  Other  methods  have  therefore 
been  used,  and  these  will  be  considered  under  mesitylene  and 
naphthalene.  It  may  be  said,  in  anticipation,  that  the  result 
of  all  observations  point  to  formula  I.  for  ortho-xylene ;  to 
formula  II.  for  meta-xylene,  and  to  formula  III.  for  para- 
xylene. 


Ethyl-benzene,  C8H10(=  CfiH5.C.2H5).  —  This  hydrocarbon  is 
isomeric  with  the  xylenes,  but  differs  from  them  in  that  it  con- 
tains an  ethyl  group  in  the  place  of  one  hydrogen  of  benzene, 


246       BENZENE  SERIES  OF  HYDROCARBONS. 

instead  of  two  methyl  groups  in  the  place  of  two  hydrogens  of 
benzene. 

It  is  made  by  treating  a  mixture  of  brom-benzene  and  ethyl 
bromide  with  sodium  :  — 

C6H5Br  +  C2H5Br  +  2  Na  =  C6H5.C2H5  +  2  NaBr. 

Its  conduct  towards  oxidizing  agents  distinguishes  it  from  the 
xylenes.  It  yields  benzoic  acid,  just  as  toluene  does.  In  this 
case,  as  in  that  of  toluene,  the  paraffin  radical  is  converted  into 
carboxyl.  It  has  been  found  that  no  matter  what  this  radical 
may  be,  it  is,  under  the  same  circumstances,  converted  into  car- 
boxyl. Thus,  the  conversions  indicated  below  take  place  :  — 

C6H5.CH3  gives  C6H5.C02H. 

C6H5.C2H5         "  C6H5.C02H. 

C6H5 .  C3H7  C6H5 .  CO2H . 

CeH5 .  CsHu        ' '  C6H5 .  CO2H . 


Mesitylene,  C9H12[=CGH:3(CH3)3].  —  Mesitylene  is  contained 
in  small  quantity  in  light  oil,  and  may  be  obtained  in  pure  con- 
dition from  this  source.  It  is  most  readily  prepared  by  treating 
acetone  with  sulphuric  acid  :  — 

3  C3H60  =  C9H12  +  3  H20. 


It  is  a  liquid  resembling  the  lower  members  of  the  series  in  its 
general  properties.     It  boils  at  163°. 

Its  conduct  towards  oxidizing  agents  shows  that  it  is  a  tri- 
methyl-benzene.  When  boiled  with  dilute  nitric  acid,  it  yields 
mesitylenic  acid,  C9H10O2,  and  uvitic  acid,  C9H8O4 ;  and,  by 


MESITYLENE. 


247 


further  oxidation  with  chromic  acid,  trimesitic  acid,  CgHgOg,  is 
formed.  By  distillation  with  lime,  mesitylenic  acid  yields  meta- 
xylene  and  carbon  dioxide  ;  uvitic  acid  yields  toluene  and  car- 
bon dioxide  ;  and  trimesitic  acid  yields  benzene  and  carbon 
dioxide.  .  The  formation  and  decomposition  of  the  acids  may 
be  represented  by  the  equations  following  :  — 

rCH3 
C6H3(CH3)3    +30  =  C6H3  J  CH3  +  H2O  ; 

Mesitylene.  (  ^Q^ 

Mesitylenic  acid. 

(CH3  rCH3 

C6H3  j  CH3     +30  =  C(iH3  }  C02H  +  H2O  ; 
(-CO2H  (CO2H 

Mesitylenic  acid.  Uvitic  acid. 

(  CH3  f  CO2H 

C6H3    CO2H  +  3  O  =  C6H3  1  CO2H  +  H2O  ; 

ICO2H 

Trimesitic  acid. 


Uvitic  acid. 


.C02H 

Mesitylenic  acid. 

(CH3 

C6H3  j  C02H 
ICO2H 

Uvitic  acid. 

(CO2H 

C6H3  ]  C02H 

(C02H 

Trimesitic  acid. 


=C6H4          8  + 
H3 

Meta-xylene. 

=  C6H5  .CH3  +  2  C0 


2; 


C6HG  +  3  C02. 

Benzene- 


These  transformations  show  clearly  that  mesitylene  is  tri- 
methyl-beuzene,  but  they  do  not  show  in  what  relation  the 
methyl  groups  stand  to  each  other. 

An  ingenious  speculation  in  regard  to  this  relation  is  based 
upon  the  fact  that  mesitylene  is  formed  from  acetone.  It. 


248       BENZENE  SERIES  OF  HYDROCARBONS. 

appears  probable  that  each  of  the  three  molecules  of  acetone 
taking  part  in  the  reaction, 

3  C3H60  =  C9H12  +  3  H20, 

undergoes  the  same  change.  As  the  product  contains  three 
methyl  groups,  the  simplest  assumption  that  can  be  made  is 
that  each  acetone  molecule  gives  up  water  as  represented 
thus :  — 

CH3-CO-CH3  =  CH3-C-CH  +  H2O. 

Acetone. 

We  thus  have  three  residues,  CH3— C  — CH,  and  these  unite 
to  form  trimethyl  benzene.  The  only  way  in  which  the  union 
can  be  represented,  assuming  that  all  three  act  in  the  same 
way,  is  this  :  — 

CH3 

/C\ 
HCT      XCH 

I        I 

H3C.C\      /C.CH3 

xcr 

H 

According  to  this  reasoning,  mesitylene  is  a  symmetrical  com- 
pound,— that  is  to  say,  each  of  the  three  methyl  groups  bears 
the  same  relation  to  the  molecule  ;  and  the  same  is  true  of  each 
of  the  three  benzene-hydrogen  atoms. 

This  view  has  been  tested  by  replacing  the  three  Irydrogen 
atoms  successively  by  bromine  ;  and  it  has  been  found  that 
the  view  is  confirmed,  as  but  one  mono-bromine  substitution- 
product  of  mesitylene  has  ever  been  obtained.  Accepting  the 
formula  above  given  for  mesitylene,  an  important  conclusion 
follows  regarding  the  nature  of  meta-xylene.  For  we  have 
seen  that,  by  oxidizing  mesitylene,  we  get,  as  the  first  product, 
mesitylenic  acid,  —  which  is  mesitylene,  one  of  whose  methyls, 
has  been  converted  into  carboxyl.  As  all  the  methyl  groups 


PSEUDOCUMENE.  249 

bear  the  same  relation  to  the  molecule,  it  makes  no  difference 
which  one  is  oxidized.     The  acid  has  the  formula 

CH3 

TT/^  /      \  r^tr 
111^  Orl 

I  I 

CO2H.CX    /C.CHg 
H 

Now,  by  distilling  this  acid  with  lime,  carbon  dioxide  is  given 
off,  and  meta-xj'lene  is  produced. 

As  the  change  consists  in  removing  the  carboxyl,  and  replac- 
ing it  by  hydrogen,  it  follows  that  meta-xylene  must  be  repre- 
sented by  the  formula 

CH3 

,G\ 
UC/    XCH 

1  I 

\^/ 


and  consequently  that,  in  all  meta  compounds,  the  two  substi- 
tuting atoms  or  groups  bear  to  each  other  the  relation  which  the 
two  methyl  groups  bear  to  each  other  in  this  formula  for  meta- 
xylene. 

Pseudocumene,  C9Hi2l>  C6H3(CH3)3].  —  This  hydrocarbon, 
which  is  isomeric  with  mesitylene,  occurs  in  coal-tar  oil,  from 
which  it  can  be  made  in  pure  condition.  Its  properties  are 
similar  to  those  of  the  lower  members  of  the  series.  It  boils 
at  169.8°. 

Pseudocumene  has  been  made  synthetically  from  brom-para- 
xylene  and  methyl  iodide,  and  also  from  brom-meta-xylene  and 


250       BENZENE  SERIES  OF  HYDROCARBONS. 

methyl  iodide.     How  this  is  possible,  will  be  understood  by  an 
examination  of  the  formulas  below  :  — 

CH3  CH3 

HCX    XCH  HC/    XCH 

II  II 

HCX     /CEr  HCX     /C.CH3 

^c'  x<r 

CH  ^r 

Brom.para-x|lene.  Brom-meta-xylene. 

Replacing  the  bromine  by  methyl,  in  either  of  the  compounds 
represented,  the  product  would  have  the  formula 


CHS 


CH 

I  . 


CH3 

which  is  that  of  pseudocumene. 


Cymene,  |  C10Huf  C  H 

Para-methyl-propyl-benzene,  /  u\  '  C3H7 
This  hydrocarbon  is  of  special  importance  and  interest,  on 
account  of  its  close  connection  with  two  well-known  groups 
of  natural  substances, — the  groups  of  which  camphor  and  oil 
of  turpentine  are  the  best-known  representatives.  It  occurs  in 
the  oil  of  caraway  and  the  oil  of  thyme.  The  terpenes,  which 
are  hydrocarbons  of  the  formula  C10H16,  and  of  which  oil  of 
turpentine  is  the  best  known,  easily  give  up  two  hydrogen 
atoms  and  yield  cymene.  Probably  the  simplest  wa}r  to  pre- 
pare cymene  is  to  treat  camphor  with  phosphorus  pentasul- 
phide,  zinc  chloride,  or  phosphorus  pentoxide. 
It  is  a  liquid  of  a  pleasant  odor.  It  boils  at  175°. 


CYMENE.  251 

It  has  been  made  synthetically  from  para-brom-toluene  and 
propyl  bromide  :  — 

3   +  C3H7Br  +  2  Na 


2NaBr, 


which  clearly  shows  its  relation  to  benzene.  As  the  final 
product  of  its  oxidation,  it  yields  para-phthalic  (terephthalic) 
acid  :  — 

c'H'<c£  give8  W<CO!H; 

gee  p.  246. 


CHAPTER    XV. 

DERIVATIVES    OF  THE   HYDROCARBONS,  CnH2n-c, 
OP    THE    BENZENE    SERIES. 

RECALLING  what  we  learned  under  the  head  of  Derivatives  of 
the  Paraffins,  we  naturally  look  for  representatives  of  all  the 
classes  of  compounds  there  met  with.  The  derivatives  of  the 
paraffins  were  classified  into  :  — 

1.  Halogen  derivatives. 

2.  Oxygen    derivatives,    including    the   Alcohols,    Aldehydes, 

Acids,  etc. 

3.  Sulphur  derivatives,   including   the   Mercaptans,   Sulphonic 

Acids,  etc. 

4.  Nitrogen  derivatives,  including  Cyanides,  Amines,  Nitro  com- 

pounds, etc. 

5.  Metallic  derivatives. 

The  derivatives  of  the  benzene  hydrocarbons  may  be  classi- 
fied in  the  same  way,  but  a  change  in  the  order  of  consideration 
will  be  somewhat  more  convenient  in  this  connection,  owing  to 
many  points  of  analogy  which  exist  between  the  halogen  sub- 
stitution-products, the  nitro  compounds,  and  the  sulphonic 
acids.  All  of  these  three  classes  of  derivatives  of  the  benzene 
hydrocarbons  are  made  by  direct  treatment  of  the  hydrocarbons 
with  the  substituting  agents,  and  in  some  respects  resemble 
each  other,  so  that  they  will  be  considered  in  connection.  As 
the  amido  derivatives  of  this  series  are  made  almost  exclusively 
from  the  nitro  compounds  by  reduction,  they  will  be  considered 
in  connection  with  the  nitro  compounds  ;  and,  further,  by  treat- 
ment of  the  amido  compounds  with  nitrous  acid,  a  new  class 


HALOGEN   DERIVATIVES    OF    BENZENE.  253 

of  nitrogen  derivatives,  known  as  diazo  compounds,  not  met 
with  in  connection  with  the  paraffins,  is  formed.  These  will 
be  considered  after  the  amido  compounds. 

After  these  classes  have  been  considered,  we  shall  take  up  in 
turn  the  oxygen  derivatives,  which  include  the  phenols  or  simple 
hydroxyl  derivatives  of  the  hydrocarbons,  the  alcohols,  alde- 
hydes, acids,,  and  ketones ;  and,  finally,  the  hydroxy-acids, 
which  are  strictly  analogous  to  the  hydroxy-acids  of  the  paraffin 
series. 

We  have  thus  the  following  classes  :  — 

1.  Halogen  derivatives.  5.  Sulphonic  acids.      9.  Acids. 

2.  Nitro  compounds.  6.  Phenols.  10.  Ketones  (and 

3.  Amido  compounds.  7.  Alcohols.  Quinones). 

4.  Diazo  compounds.  8.  Aldehydes.  11.  Hydroxy-acids. 

The  relations  of  most  of  these  classes  to  the  hydrocarbons 
are  the  same  as  those  of  the  corresponding  derivatives  of  the 
paraffin  series  to  the  paraffins ;  and  the  general  methods  of 
preparation,  as  well  as  the  reactions,  are  the  same.  Hence, 
most  of  the  knowledge  acquired  in  the  first  part  of  the  book 
may  be  applied  to  the  series  now  under  consideration. 

An  enormous  number  of  derivatives  of  the  benzene  hydrocar- 
bons have  been  prepared  and  studied ;  but  we  need  study  only 
very  few  in  order  to  acquire  a  general  knowledge  of  them.  In 
the  following  a  few  of  the  more  important  representatives  of 
each  class  will  be  studied,  mainly  with  the  object  of  illustrating 
general  facts  and  general  relations. 

HALOGEN  DERIVATIVES  OF  BENZENE. 

Very  little  need  be  said  in  regard  to  these  derivatives.  By 
direct  action  of  bromine  or  chlorine  upon  benzene  the  hydrogen 
atoms  are  replaced  one  after  another,  until,  as  the  final  products, 
hexa-chlor-benzene,  C6C\Q,  and  hexa-brom-benzene,  C6Br6,  are  ob- 
tained. It  has  already  been  stated  that,  when  the  action  takes 


254  DERIVATIVES   OF   THE  BENZENE   SERIES. 

place  in  direct  sunlight,  addition-products,  C6H6C16  and  C6H6Br6, 
are  formed.  Benzene  hexachloride,  C6H6C16,  is  formed  also 
when  chlorine  is  conducted  into  boiling  benzene.  The  addition- 
products  are  readily  decomposed,  yielding  tri-substitution  prod- 
ucts of  benzene  and  halogen  acid  :  — 

C6H6Br6  =  C6H3Br3  +  3  HBr. 

The  substitution-products  are  very  stable.  They  are,  as  a 
rule,  formed  more  easily  than  the  halogen  derivatives  of  the 
paraffins,  and,  as  a  rule,  they  do  not  give  up  the  halogens  as 
readily.  Thus,  while  it  is  possible  in  the  paraffin  demratives 
to  replace  chlorine  and  bromine  by  hydroxyl,  the  amido  group, 
etc.,  these  replacements  cannot  easily  be  effected  in  the  benzene 
derivatives.  The  halogens  can  be  removed  by  sodium,  as 
shown  in  the  synthesis  of  hydrocarbons  :  — 

C6H5Br  +  CH3I  +  2  Na 
=  C6H5.CH3  -f-  NaBr  -f  Nal,  etc.,  etc. 

They  may  also  be  removed  by  nascent  hydrogen,  the  hydro- 
carbons being  regenerated :  — 

C6H4C12  -f  4  H  =  C6H6  +  2  HC1. 

This  kind  of  reverse  substitution  is  not,  however,  effected 
easily. 

Perhaps  the  best  known  of  the  di-substitution  products  of  the 
class  under  consideration  is 

Dibrom-benzene,  C6H4Br2,  which  is  one  of  the  products  of 
the  direct  treatment  of  benzene  with  bromine.  This  being  a 
di-substitution  product  of  benzene,  it  follows,  from  what  has 
been  said  in  regard  to  isomerism  in  this  group,  that  three 
isomeric  varieties  of  the  substance  ought  to  be  obtainable  ;  and 
the  interesting  question  suggests  itself :  which  one  of  the 
three  possible  dibrom -benzenes  is  formed  by  direct  treatment  of 
benzene  with  bromine  ?  The  answer  to  the  question  is  equally 


HALOGEN  DERIVATIVES  OF  TOLUENE.       255 

interesting.  The  main  product  of  the  action  is  para-dibrom- 
benzene,  while  there  is  always  formed  in  much  smaller  quantity 
some  of  the  ortho  product.  The  reason  why  these  products 
are  obtained,  and  not  the  meta  compound,  is  unknown ;  nor 
has  any  plausible  hypothesis  been  suggested  to  account  for  the 
fact. 

In  stud}'ing  the  substitution-products  of  benzene,  one  of  the 
first  problems  which  present  themselves  is  the  determination 
of  the  relations  which  the  substituting  atoms  or  groups  bear 
to  each  other.  The  determination  is  made,  as  has  been 
stated,  by  transforming  the  compounds  into  others,  the  rela- 
tions of  whose  groups  are  known.  Thus,  to  illustrate,  when 
benzene  is  treated  under  the  proper  conditions  with  bromine, 
two  dibrom-benzenes  are  formed.  Without  investigation,  we, 
of  course,  cannot  tell  to  which  series  these  compounds  belong. 
But,  by  treating  that  product  which  is  formed  in  larger  quantity 
with  methyl  iodide  and  sodium,  we  get  para-xylene.  In  other 
words,  by  replacing  the  two  bromine  atoms  of  the  dibrom- 
benzene  by  methyl  groups,  we  get  a  compound  which  we  know 
belongs  to  the  para  series  ;  and,  therefore,  we  have  determined 
that  the  bromine  product  is  a  para  compound.  In  the  follow- 
ing the  chief  reactions  made  use  of  for  effecting  the  trans- 
formations of  the  derivatives  will  be  discussed. 

HALOGEN  DERIVATIVES  OF  TOLUENE. 

As  toluene  is  made  up  of  a  residue  of  marsh  gas,  methyl,  CH3, 
and  a  residue  of  benzene,  phenyl,  C6H5,  it  might  naturally  be 
expected  that  it  would  yield  two  classes  of  substitution-prod- 
ucts:  viz.,  (1)  Those  in  which  the  substituting  atom  or  group 
replaces  one  or  more  hydrogen  atoms  of  the  phenyl  group ; 
and  (2)  those  in  which  the  substitution  takes  place  in  the 
methyl.  Representatives  of  both  these  classes  are  well  known. 
In  general,  when  boiling  toluene  is  treated  with  chlorine  or 
bromine,  products  of  the  second  class  are  obtained;  while. 


256  DERIVATIVES   OF   THE   BENZENE   SERIES. 

when  treated  in  the  cold,  products  of  the  first  class  are  ob- 
tained. Thus,  we  have  the  two  parallel  series  of  chlorine 
derivatives  :  — 

i.  n. 

C6H4C1.CH3.  C6H5.CH2C1. 

C(jH3Cl2  .CH3.  ^6^5  .CHC12. 

C6H2C13.CH3.  C6H5.CC13. 

When  a  member  of  the  first  class  is  oxidized,  the  methyl  is 
changed,  and  the  rest  of  the  compound  remains  unchanged, 
as  in  the  case  of  toluene.  Thus,  the  first  substance  of  class  I. 
yields  the  product  C6H4C1.CO2H;  the  second,  C6H3C12.CO2H, 
etc.  These  products  are  substituted  benzole  acids.  On  the 
other  hand,  all  the  members  of  the  second  class  yield  the  same 
product  that  toluene  does;  viz.,  benzoic  add.  Hence,  by 
treatment  with  oxidizing  agents,  it  is  easy  to  distinguish  between 
the  members  of  the  two  classes.  Further,  the  halogen  atoms 
contained  in  the  methyl  are  not  as  firmly  held  in  combination 
as  those  in  the  phenyl.  When,  for  example,  the  compound 
C6H5.CHC12,  which  is  called  benzal  chloride,  is  treated  with 
water,  both  chlorine  atoms  are  replaced  by  oxygen,  the  product 
being  the  aldehyde  C6H5.CHO,  which,  as  we  shall  see,  is  the 
familiar  substance,  oil  of  bitter  almonds.  When,  however,  the 
isomeric  di-chlor-toluene  C6H3Cl2.CHjj  is  heated  with  water,  no 
change  takes  place. 

Regarding  those  simple  substitution-products  of  toluene  which 
contain  one  halogen  atom  in  the  phenyl,  such  as  mono-brom- 
toltiene,  C6H4Br.CH3,  we  see  that  they  are  di-substitution  prod- 
ucts of  benzene,  and  hence  capable  of  existing  in  three  isomeric 
varieties,  ortho,  meta,  and  para.  The  products  formed  by 
direct  treatment  of  toluene  with  chlorine  or  bromine  are  mixtures 
consisting  mostly  of  the  para  compound,  together  with  a  much 
smaller  quantit}r  of  the  ortho  compound. 

The  determination  of  the  series  to  which  one  of  these  products 
belongs  may  be  made  by  replacing  the  halogen  by  methyl,  and 


NITPO   COMPOUNDS    OF   BENZENE   AND   TOLUENE.     257 

thus  getting  the  corresponding  xylene.  The  main  product  of 
the  action  of  bromine  on  toluene  is  thus  converted  into  para- 
xylene,  and  is  therefore  para-brom- toluene. 

HALOGEN  DERIVATIVES  OF  THE  HIGHER  MEMBERS  OF 
THE  BENZENE  SERIES. 

Concerning  the  halogen  derivatives  of  xylene,  it  need  only  be 
said  that  the  only  one  of  the  three  xylenes  from  which  pure 
products  can  easily  be  obtained  is  para-xylene.  When  this  is 
treated  with  bromine  it  yields  but  one  mono-brom-xylene.  The 

significance  of  this  fact  has  been  discussed  above.     The  mono- 

& 

substitution  products  obtained  from  the  other  xylenes  are 
mixtures  which  it  is  very  difficult,  and  in  some  cases  impos- 
sible, to  separate  into  their  constituents.  Mesitylene  and 
pseudocumene,  though  both  are  tri-methyl-benzenes,  conduct 
themselves  quite  differently  towards  bromine, — the  former  yield- 
ing only  one  mono-bromine  product ;  the  latter,  a  mixture  of 
several. 

NITRO  COMPOUNDS  OF  BENZENE  AND  TOLUENE. 

In  speaking  of  nitro  compounds  in  connection  with  the  paraf- 
fin derivatives  (see  p.  100),  it  was  stated  that  they  are  obtained 
much  more  readily  from  the  benzene  hydrocarbons  than  from 
the  paraffins.  But  few  nitro  derivatives  of  the  paraffins  are 
known.  As  will  be  remembered,  they  cannot  be  prepared  by 
treating  the  paraffins  with  nitric  acid,  but  must  be  made  by 
circuitous  reactions,  the  principal  one  being  the  treatment  of 
the  halogen  derivatives  with  silver  nitrite  :  — 

C2H5Br  -f  AgNO2  =  C2H5(NO2)  +  AgBr. 

Nitro-e  thane. 

The  preparation  of  a  nitro  derivative  of  a  hydrocarbon  of 
the  benzene  series  is  a  simple  matter.  It  is  only  necessary  to 
bring  the  hydrocarbon  in  contact  with  strong  nitric  acid,  when 
reaction  takes  place,  and  one  or  more  hydrogen  atoms  of  the 


258  DERIVATIVES    OF    THE   BENZENE    SERIES. 

hydrocarbon  are  replaced  by  the  nitro  group  NQ2,  as  illustrated 
in.  the  equations,  — 

C6H6  +  HN03  -  CCH5  .  N02         +  H2O  ; 

C6H5.N02     +  HN08  =  C6H4(N02)2      +  H2O  ; 

ivo 

C6H5  .CH3      +  HN08  =  C6H4  <  ££*       +  H2Q  ; 

U±i3 

HN08  =  C6H3  <      °2)2  +  H20. 


The  nitro  compounds  thus  obtained  are  not  acids,  nor  are 
they  ethereal  salts  of  nitrous  acid,  as  the  formulas  might  lead 
us  to  suppose.  The  most  rational  view  held  in  regard  to  them 
is,  that  .they  are  formed  from  nitric  acid  by  the  replacement  of 
hydroxyl  by  benzene  radicals,  as  indicated  thus  :  — 

C6H5!H  THOJ.NO2  =  C6H5.NO2  +  H2O. 

Mono-nitro-benzene,  C6H5.NO2.  —  This  substance  is  made 
by  treating  benzene  with  concentrated  nitric  acid,  or  with  a 
mixture  of  ordinary  concentrated  nitric  'and  sulphuric  acids. 
In  the  latter  case,  the  sulphuric  acid  facilitates  the  reaction, 
probably  by  preventing  the  dilution  of  the  nitric  acid  by  the 
water  necessarily  formed. 

Experiment  58.  Make  a  mixture  of  150CC  ordinary  concentrated 
sulphuric  acid,  and  75CC  ordinary  concentrated  nitric  acid.  Let  it  cool 
to  the  ordinary  temperature.  Put  the  vessel  containing  it  in  water, 
and  add  about  15CC  to  20CC  benzene,  a  few  drops  at  a  time,  waiting  each 
time  until  the  reaction  is  complete.  Shake  well  until  the  benzene  is 
dissolved;  then  pour  slowly  into  about  a  litre  of  cold  water.  A  yellow 
oil  will  sink  to  the  bottom.  This  is  nitre-benzene.  Pour  off  the  acid 
and  water  ;  wash  two  or  three  times  with  water  ;  separate  the  water 
by  means  of  a  pipette,  and  dry  by  adding  a  little  granulated  calcium 
chloride.  After  standing  for  some  time,  pour  off  from  the  calcium 
chloride,  and  distil  from  a  proper  sized  distilling-bulb,  noting  the 
boiling  temperature. 

Nitro-benzene  is  a  liquid  which  boils  at  205°,  and  has  the 


EITRO-TOLUENES.  259 

specific  gravity  1.2.  Its  odor  is  like  that  of  the  oil  of  bitter 
almonds,  and  it  is  hence  used  in  many  cases  instead  of  the 
latter.  It  is  known  as  the  essence  of  mirbane.  It  is  manufac- 
tured on  the  large  scale,  and  used,  principally  in  the  preparation 
of  aniline. 

Dinitro-benzene,  C6H4(NO2)2.  —  This  is  a  product  of  the 
further  action  of  nitric  acid  on  benzene,  or  on  nitro-benzeue. 

Experiment  59.  Make  a  mixture  of  50CC  concentrated  sulphuric 
acid,  and  50CC  fuming  nitric  acid.  Without  cooling  add  very  slowly 
about  10CC  benzene  from  a  pipette  with  a  fine  opening.  After  the 
action  is  over,  boil  the  mixture  for  a  short  time ;  then  pour  into  about 
half  a  litre  of  water.  Filter  off  the  solid  substance  thus  precipitated, 
press  it  between  layers  of  niter-paper,  and  crystallize  from  alcohol. 

Dinitro-benzene  crystallizes  in  long,  fine  needles,  or  thin, 
rhombic  plates.  Melting-point,  89.9°. 

By  means  of  two  reactions,  which  will  be  considered  under 
the  head  of  Diazo  Compounds,  it  is  a  simple  matter  to  replace 
the  two  nitro  groups  by  bromine,  thus  converting  dinitro-ben- 
zene  into  bibrom-benzene.  When  the  latter  is  converted  into 
xylene,  the  product  is  meta-xylene.  Hence,  ordinary  dinitro- 
benzene  is  a  meta  compound. 

Nitro-toluenes,  C6H4(NO2).CH3. — When  toluene  is  treated 
with  strong  nitric  acid,  substitution  always  takes  place  in  the 
phenyl.  The  chief  mono-nitro-toluene  is  a  para  compound ; 
while,  at  the  same  time,  a  little  of  the  isomeric  ortho  compound 
is  obtained. 

NOTE  FOR  STUDENT.  —  What  mono-bromine  products  are  formed 
by  direct  treatment  of  toluene  with  bromine  ?  Given  a  mono-nitro- 
toluene,  how  is  it  possible  to  determine  whether  it  belongs  to  the 
ortho,  the  meta,  or  the  para  series? 

By  treatment  with  nascent  hydrogen,  the  nitro-toluenes  are 
converted  into  the  corresponding  amido  compounds,  called 
Toluidines  (which  see) . 


260  DERIVATIVES   OF  THE  BENZENE   SERIES, 

AMIDO  COMPOUNDS  OF  BENZENE,  ETC. 

The  amido  derivatives  of  the  paraffins  are  made,  for  the  most 
part,  by  treating  the  halogen  derivatives  with  ammonia :  — 

C2H5Br  +  NH3  =  C2H5.NH2  +  HBr. 

Iii  speaking  of  these  derivatives,  however,  attention  was  called 
to  the  fact  that  they  may  also  be  made  by  treating  nitro  com- 
pounds with  nascent  hydrogen.  The  latter  method  is  one  of 
great  importance  in  the  benzene  series.  It  is  used  exclusively 
in  the  preparation  of  the  amido  derivatives  of  the  benzene 
hydrocarbons.  Several  of  these  derivatives  are  well  known, 
the  simplest  and  best  known  being  amido-benzene  or  aniline. 

Aniline,  C6HTN(=  CGH5.NH2).  —  Aniline  was  first  obtained 
from  indigo  by  distillation.  Anil  is  the  Portuguese  and  French 
name  of  the  indigo  plant,  and  it  is  from  this  that  the  name 
aniline  is  derived.  Aniline  is  found  in  coal  tar  and  in  bone  oil, 
a  product  of  the  distillation  of  bones.  It  is  prepared  by  re- 
duction of  nitro-benzene  with  nascent  hydrogen.  On  the  large 
scale  the  hydrogen  is  obtained  from  hydrochloric  acid  and  iron. 
For  laboratory  purposes  tin  and  hydrochloric  acid  are  perhaps 
best.  Other  reducing  agents,  such  as  an  ammoniacal  solution 
of  ammonium  sulphide,  hydriodic  acid,  etc.,  also  effect  the 
change,  which  is  represented  by  the  following  equation  :  — 

C6H5.NO2  -f-  6H  =  C6H5.NH2  +  2H2O. 

Experiment  6O.  Dissolve  the  nitro-benzene  obtained  in  Exp.  58 
in  alcoholic  ammonia,  and  saturate  the  solution  with  hydrogen  sul- 
phide, keeping  it  slightly  warm.  On  the  water-bath  distil  off  the  excess 
of  ammonium  sulphide  and  some  of  the  alcohol.  To  the  residue  add 
dilute  hydrochloric  acid.  This  will  dissolve  the  aniline,  but  leave 
any  unchanged  nitro-benzene  undissolved.  Separate  the  latter.  Evapo- 
rate to  dryness ;  mix  with  a  little  lime,  and  distil  from  a  dry  vessel. 
Aniline  will  pass  over. 

Aniline  is  a  colorless  liquid  which  rapidly  becomes  colored  in 


TOLUIDINES.  261 

the  air.  It  boils  at  184.5°.  It  solidifies  at  a  low  temperature  ; 
is  easily  soluble  in  alcohol,  but  slight!}-  soluble  in  water.  The 
solution  in  water  has  only  a  very  slight  alkaline  reaction. 

Experiment  61.  To  an  aqueous  solution  of  a  little  of  the  aniline 
obtained  in  Exp.  CO,  in  a  test-tube,  add  a  filtered  solution  of  bleach- 
ing powder  (calcium  hypochlorite).  A  beautiful  purple  color  is  pro- 
duced. 

To  a  solution  of  aniline  in  concentrated  sulphuric  acid  add  a  few 
drops  of  an  aqueous  solution  of  potassium  bichromate.  A  blue  color 
is  produced. 

Aniline  bears  to  benzene  the  same  relation  that  ethyl-amine 
or  amide-ethane  bears  to  ethane.  It  is  a  substituted  ammonia, 
and,  like  other  bodies  of  the  same  class,  it  unites  directly  with 
acids,  forming  salts.  Thus,  with  hydrochloric,  nitric,  and 
sulphuric  acids  the  action  takes  place  as  represented  below  :  — 

C6H5  .  NH2  +  HC1      =  (C6H5  .  NH3)  Cl  ; 
C6H5.NH2  +  HN08  =  (C6H5.NH3)N03; 
C6H5  .  NH2  +  H2S04  =     CGH5  .  NH3HSO4. 

The  formation  of  aniline  h4ydrochloride  was  illustrated  in 
Exp.  60,  as  was  also  the  decomposition  of  an  aniline  salt  by 
a  caustic  alkali  :  — 

2  (C6H5  .  NH3)  Cl  +  Ca  (OH)  a  =  2  C6H5  .  NH2  +  2  H2O  +  CaCl2. 

Among  the  most  interesting  changes  which  can  be  effected  in 
aniline  is  that  which  takes  place  when  it  is  treated  with  nitrous 
acid  (see  Diazo  Compounds,  below). 

NOTE  FOR  STUDENT.  —  What  change  is  usually  effected  in  amido 
compounds  by  treating  them  with  nitrous  acid? 


Toluidines,   arnido-toluenes,   GJI±  <        2.  —  The    tolui- 

CH3 
dines,  of  which  there  are  three  corresponding  to  the  three  nitro- 

toluenes,  are  made  from  the  latter  in  the  same  way  that  aniline 
is  made  from  nitre-benzene.    As  pam-nitro-toluene  is  the  best 


262  DERIVATIVES    OF   THE   BENZENE   SERIES. 

known  of  the  three  nitro-toluenes,  so  para-toluidine  is  the  best 
known  of  the  three  toluidines. 

The  properties  of  the  toluidines  are  much  like  those  of  aniline. 

Treated  with  various  oxidizing  agents,  a  mixture  of  aniline 
and  the  toluidines  is  converted  into  a  compound  known  as 
rosaniline.  This  is  the  mother  substance  of  the  large  group  of 
compounds  known  as  the  aniline  dyes.  Rosaniline  and  its  de- 
rivatives, the  aniline  dyes,  will  be  considered  under  Tri-phenyl- 
methane  (which  see)  . 

By  nitrous  acid  the  toluidines  are  transformed  in  the  same 
way  that  aniline  is  (see  Diazo  Compounds). 

The  xylidines  bear  to  the  three  xylenes  the  same  relation 
that  aniline  bears  to  benzene.  It  is  not  a  simple  matter  to  get 
any  one  of  them  in  pure  condition. 

DIAZO  COMPOUNDS  OF  BENZENE,  ETC. 

The  usual  action  of  nitrous  acid  on  amido  compounds  is 
represented  by  the  equation,  — 

R  .  NH2  +  HNO2  =  R  .  OH  +  H2O  +  N2. 

When  an  amido  derivative  of  a  hydrocarbon  of  the  benzene 
series  is  treated  with  nitrous  acid,  and  certain  precautions  are 
taken,  a  product  is  obtained  which  contains  two  nitrogen 
atoms,  and  which  is,  therefore,  called  a  diazo  compound. 
Thus,  in  the  case  of  aniline  sulphate,  the  action  is  represented 
by  the  equation,  — 

CGH5NH2.H2SO4  +  HNO2  =  C6H5N2.HSO4  +  2  H2O. 

Aniline  sulphate.  Diazo-benzene  sulphate. 

So,  also,  with  the  nitrate  we  have,  — 


C6H5NH2.HNO3  +  HNO2  =  CcBtN2.NO8  +  2  H2O. 

Aniline  nitrate.  Diazo-benzene  nitrate. 

From  these  salts  the  diazo-benzene  itself  can  be  set  free  by 
means  of  acetic  acid.     It  has  been  found  to  have  the  formula 


DIAZO  COMPOUNDS  OF  BENZENE,  ETC. 


263 


C6H5N2(OH).     This  compound  is,  however,  very  unstable,  and 
is  at  once  decomposed. 

Experiment  62.  Arrange  an  apparatus  as  shown  in  Fig.  14.  In 
flask  A  put  some  coarsely-powdered  arsenic  trioxide  (about  50s),  and 
through  the  funnel-tube  pour  40CC  to  50CC  ordinary  nitric  acid  of  specific 
gravity  1.35.  B  is  an  empty  cylinder  surrounded  by  water.  Cand  D 
are  small  flasks  of  about  50CC  capacity,  in  each  of  which  should  be 
brought  10s  aniline  nitrate,  and  12CC  ice-cold  water. 


Fig.  14. 


They  are  kept  in  ice  water.  Pass  a  current  of  the  oxides  of  nitrogen 
until  the  material  in  the  flasks  dissolves.  Add  to  the  solution  about 
an  equal  volume  of  alcohol  previously  cooled  to  0°,  and  then  a  little  cold 
ether.  If  the  operation  has  been  carried  out  properly,  a  copious  pre- 
cipitate of  crystals  of  diazo-benzene  nitrate  is  formed.  Filter  off  with 
the  aid  of  a  suction-pump,  and,  without  delay,  proceed  to  study  the 
properties  of  the  compound. 

(a)  Dissolve  a  little  in  water  of  the  ordinary  temperature,  and  allow 


264  DERIVATIVES   OF   THE  BENZENE   SERIES. 

the  solution  to  stand.  Decomposition,  indicated  by  change  of  color, 
will  take  place. 

(6)  Boil  a  little  with  water  in  a  test-tube,  and  notice  the  odor  of 
phenol  or  carbolic  acid. 

(c)  Boil  a  few  grams  with  alcohol  in  a  test-tube,  and  notice  the  ease 
with  which  the  decomposition  takes  place.  The  chief  product  is  ethyl- 
phenyl  ether  or  phenetol,  C6H5 .  O  .  C2H3. 

(cT)  Boil  some  with  hydrochloric  acid.  Chlor-benzene  is  formed, 
which  sinks  to  the  bottom  when  water  is  added. 

In  all  these  experiments  a  gas  is  evolved  which  can  be  shown  to  be 
nitrogen.  Collect  so'me,  and  show  that  it  does  not  support  combustion, 

(e)  Place  a  very  little  of  the  compound,  dried  by  pressing  in  filter- 
paper,  on  an  anvil,  and  strike  it  sharply  with  a  hammer.  It  explodes. 

The  above  experiments  serve  to  indicate  the  instability  of 
diazo-benzene  nitrate.  This  same  instability  is  characteristic 
of  all  diazo  compounds,  and  it  is  the  ease  with  which  they 
undergo  a  variety  of  changes  that  makes  them  so  valuable. 
The  principal  changes  are  :  — 

1.  That  illustrated  in  Exp.  62   (5),  which*  is  brought  about 
by  boiling  with  water.     The  action  is  represented  thus  :  — 

C6H5N2 .  N03  +  H20  =  C6H5 .  OH  +  N2  +  HNO3. 

Phenol. 

2.  That  illustrated  in  Exp.  62  (c),  which  is  effected  by  boil- 
ing with  alcohol :  - — 

C6H5N2 .  N03  +  C2H5 .  OH  =  C6H5 . 0 .  C2H5  +  N2  +  HNO3. 

Phenetol. 

3.  That  effected  by  hydrochloric  acid  as  illustrated  in  Exp. 
62  («J):_ 

C6H5N2.N08  +  HC1  =  C6H5C1  +  N2  +  HNOS. 

Mono-chlor-benzene. 

Changes  similar  to  the  last  are  effected  by  hydrobromic  and 
hydriodic  acids,  the  chief  products  being  brom-benzene  and 
iodo-benzene  respectively. 

From  the  above  it  follows  that,  if  we  have  a  compound  con- 
taining a  nitro  group,  we  can,  by  making  the  diazo  compound, 


SULPHONIC    ACIDS    OF    BENZENE,   ETC.  265 

transform  it  (1)  into  the  corresponding  hydroxyl  derivative; 
(2)  into  the  corresponding  chlorine,  bromine,  or  iodine  deriva- 
tive ;  or,  (3)  we  can  make  ethers  containing  such  groups  as 
C2H5O,  CH3O,  etc.  These  reactions  involving  the  use  of  the 
clinzo  compounds  have  been  used  very  extensively  in  the  inves- 
tigation of  the  substitution-products  of  the  benzene  series. 

NOTE  FOR  STUDENT.  —  How  can  the  relation  of  the  groups  in  di- 
nitro-benzene  be  determined  by  using  the  diazo  reactions? 

As  regards  the  relation  of  diazo-benzene  to  benzene,  it  seems 
clear,  from  the  reactions  above  considered,  that  in  it  the  phenyl 
group  C6H3  is  present,  and  that  this  is  in  combination  with  two 
nitrogen  atoms.  In  the  compounds,  the  two  atoms  of  nitrogen 
form  the  connecting  link  between  the  phenyl  group  and  the 
other  constituent,  as  expressed  in  the  formulas 

C6H5-N2-N03, 
C6H5-N2-OK, 
C6H5-N2-Br,  etc. 

The  decompositions  all  indicate  the  correctness  of  this  view. 
How  the  nitrogen  atoms  are  united,  we  do  not  know. 

STJLPHONTC  ACIDS  OP  BENZENE,  ETC. 

The  methods  of  preparation  of  the  sulphonic  acids,  and  the 
relations  of  these  acids  to  the  hydrocarbons,  were  considered 
pretty  fully,  in  connection  with  the  paraffins.  Three  general 
methods  for  their  preparation  were  given.  These  are  :  — 

1.  Oxidation  of  the  mercaptans ;  thus,  ethyl-sulphonic  acid 
is  formed  by  oxidation  of  ethyl-mercaptan,  — 

C2H5.SH  +  3  O  =  C2H5.SO3H. 

2.  Treatment  of  a  halogen  substitution-product  with  a  sul- 
phite,— 

C2H5Br  +  Na2S03  =  C2H5.SO3Na  +  NaBr. 


266  DERIVATIVES   OF   THE  BENZENE   SERIES. 

3.  Treatment  of  a  hydrocarbon  with  sulphuric  acid.  This 
method  is  not  applicable  to  the  paraffins,  but  is  the  one  used 
almost  exclusively  in  the  case  of  the  benzene  hydrocarbons. 
Benzene-sulphonic  acid  is  formed  thus  :  — 

C6H6  +  H2S04  =  C6H5.S03H  +  H2O. 
Toluene-  sulphonic  acid  is  formed  thus  :  — 

C6H5.CH3  +  H2S04  =  C6H4<CH3     +  H20. 

bU3H 

The  reasons  for  regarding  the  sulphonic  acids  as  sulphuric 
acid  in  which  hydroxyl  is  replaced  by  radicals,  were  given  on 
p.  76  ;  and  the  student  is  advised  carefully  to  re-read  what 
is  there  said. 

Benzene-sulphonic  acid,  C6H6SO3f  =  S?5  }  SO2Y  —  This 

V     ±±<J   )         I 


acid  is  made  most  readily  by  treating  benzene  with  ordinary 
concentrated  sulphuric  acid. 

Experiment  63.  In  a  flask  bring  together  about  50CC  benzene  and 
100CC  concentrated  sulphuric  acid  (ordinary).  Connect  with  an  inverted 
condenser  (see  Fig.  8,  p.  70),  and  boil  for  several  hours,  until  the 
greater  part  of  the  benzene  has  passed  into  solution.  Pour  the  con- 
tents of  the  flask  into  a  large  evaporating  dish  of  at  least  81  to  10l 
capacity,  containing  41  to  51  water.  Heat  gently,  and  add  gradually, 
stirring  mean  while,  finely-powdered  chalk,  until  the  solution  has  become 
neutral.  Pass  through  a  muslin  filter  attached  to  a  wooden  frame,  and 
wash  thoroughly  with  hot  water.  Afterwards  refilter  the  filtrate 
through  a  paper  filter.  Evaporate  to  quite  a  small  volume  (say  500CO 
to  700CC),  and  filter  from  gypsum.  In  solution  there  is  now  the  calcium 
salt  of  the  sulphonic  acid.  Add  just  enough  of  a  solution  of  potassium 
carbonate  to  precipitate  exactly  the  calcium  ;  filter  off  from  the  calcium 
carbonate,  and  evaporate  to  dryness,  finally,  on  the  water-bath.  To 
prevent  caking  it  is  necessary  to  stir  the  thick,  syrupy  mass.  When  it 
is  nearly  dry,  it  is  best  to  powder  it,  and  complete  the  drying  at  100°  to 
120°  in  an  air-bath!  The  potassium  salt  may  be  used  for  a  number  oi 
experiments. 


BENZENE-SULPHONIC   ACID.  267 

Experiment  64.  lu  a  dry  evaporating  dish  mix  thoroughly  20&  of 
potassium  beuzene-sulphonate  with  25^  of  phosphorus  penta-chloride, 
by  means  of  a  dry  pestle.  The  mass  becomes  semi-liquid  and  hot, 
and  hydrochloric  acid  is  given  off,  in  consequence  of  the  action  of  the 
moisture  of  the  air  on  the  chlorides  of  phosphorus.  Hence,  the  experi- 
ment should  be  performed  under  a  hood  or  out  of  doors.  The  reaction 
which  takes  place  is  represented  by  the  equation, — 

C6H5 .  S02OK  +  PC15  =  C6H5 .  S02C1  +  POC13  +  KC1. 

After  the  action  is  over,  and  the  mass  cooled  down  to  the  ordinary 
temperature,  add  about  a  litre  of  cold  water.  Everything  will  dissolve 
except  the  sulphon-chloride,  C6H5.  SO2C1,  which  will  remain  as  a  heavy 
oil  at  the  bottom  of  the  vessel.  Pour  off  the  greater  part  of  the  water, 
and  then  add  about  500CC  of  strong  ammonia.  The  chloride  is  thus 
converted  into  the  corresponding  sulphon-amide,  thus :  — 

CCH5 .  SO2C1  +  2  NH3  =  C6H5 .  SO2NH2  +  NII4C1. 

After  cooling,  filter  off  the  sulphon-amicle;  wash  well  with  cold  water, 
and  crystallize  from  water.  The  product  crystallizes  in  needles,  fusing 
at  153°. 

NOTE  FOR  STUDENT.  —  Refer  back  to  what  was  said  regarding  the 
acid  chlorides  and  acid  amides,  paying  particular  attention  to  the 
general  methods  of  preparation  and  their  decompositions. 

Experiment  65.  Mix  20s  potassium  cyanide  with  an  equal  weight 
of  dry  potassium  benzene-sulphonate,  and  distil  from  a  small  retort. 
The  distillate  is  impure  phenyl  cyanide,  C6H5.CN :  — 

CeH5  >  S02  +  KCN  -  C6H5  .CN  +  K2S03. 
KO 

Put  the  phenyl  cyanide  in  a  flask  of  600CC  to  700CC  capacity,  and  add 
300CC  of  a  moderately  strong  solution  of  potassium  hydroxide  in  water. 
Connect  with  an  inverted  condenser,  and  boil  for  two  or  three  hours. 
What  is  given  off?  Test  with  the  nose  the  gases  at  the  upper  end  of 
the  condenser-tube.  After  cooling,  dilute  with  about  an  equal  volume 
of  water,  and  acidify  with  hydrochloric  acid.  A  solid  substance  is 
precipitated.  Filter  off,  wash,  and  crystallize  from  water.  It  is 
benzoic  acid.  The  reaction  with  caustic  potash  is  represented  thus :  — 

C6H5.CN  +  H20  +  KOH  =  C6H5.CO2K  +  NH3. 
Benzene-sulphonic  acid  itself  is  a  very  easily  soluble  sub- 


268  DERIVATIVES   OF   THE   BENZENE   SERIES. 

stance.      It  is  a  strong  acid,  and  yields  a  series  of  salts  and 
other  derivatives. 

"When  fused  with  potassium  hydroxide,  benzene-sulphonic 
acid  is  converted  into  phenol  (Exp.  66,  p.  270)  :  — 

C6H5.SO3K  -f  KOH  =  C6H5.OH  -f  K2SO3. 

By  further  treatment  of  benzene  with  fuming  sulphuric  acid 
a  benzene-disulphonic  acid  is  formed.  This  is  capable  of  the 
same  transformations  as  the  mono-sulphonic  acid. 

NOTE  FOR  STUDENT. — By  what  reaction  could  benzene-disulphonic 
acid  betransformeclintothe  corresponding  dicarbonic  acid,C6H4(C02H);j? 
Suppose  the  product  obtained  were  meta-phthalic  acid,  what  conclusion 
could  be  drawn  with  reference  to  the  relation  of  the  two  sulpho  groups, 
S03H,  in  the  disulphonic  acid? 

PHENOLS,  OK  HYDRQXYL  DERIVATIVES  OF  BENZENE,  ETC. 

The  hydroxyl  derivatives  of  the  paraffins  are  called  alcohols. 
As  will  be  remembered  they  are  of  three  kinds,  each  of  which 
is  characterized  by  certain  properties.  We  have  :  — 

1.  Primary  alcohols  of  which  ordinary  ethyl  alcohol  is  the 
commonest  example,  and  which,  when  oxidized,  yield  aldehydes 
and  then  acids  containing  the  same  number  of  carbon  atoms. 

2.  Secondary  alcohols,  which  by  oxidation  yield  acetones  and 
then  acids  containing  a  smaller  number  of  carbon  atoms. 

3.  Tertiary  alcohols,  which  by  oxidation  yield  neither  alde- 
hydes nor  acetones,  but  break  down  at  once,  yielding  acids 
with  a  smaller  number  of  carbon  atoms. 

The    primary   alcohols   were   shown    to    correspond   to   the 

[B  (? 

formula  C  •{         ;  the  secondary  to  C  j        ;   and  the  tertiary  to 

rR       LHO  ^HO 

f  R 

CM         ;  or,  in  other  words,  the  primary  alcohols  contain  the 
E 

I  HO 
group   CH2.OH;  the  secondary,  the  group  CH.OH;   and  the 

tertiary j  the  group  C.OH. 


MON-ACTD   PHENOLS.  269 

Now,  the  simplest  hydroxyl  derivative  of  the  members  of 
the  benzene  series  is  phenol,  C6H5.OH,  or  benzene  in  which  one 
hydrogen  is  replaced  by  hydroxyl.  Representing  this  com- 
pound in  terms  of  the  accepted  benzene  hypothesis,  we  have 
the  formula 

/C\ 
IIC/     XCH 

I  I 

HCX     /CH 

xcr 

H 

According  to  this,  phenol  appears  to  be  allied  to  the  tertiary 
alcohols,  as  it  contains  the  group  C.OH,  and  not  CH2OH  nor 
CH.OH.  We  shall  see  that,  in  fact,  phenol  conducts  itself 
towards  oxidizing  agents  like  the  tertiary  alcohols. 

All  compounds  which  contain  bydroxyl  in  the  place  of  the 
benzene-hydrogen  atoms  of  benzene  and  its  homologues  are 
called  phenols.  As  in  the  case  of  alcohols,  there  are  phenols 
containing  one  hydroxyl,  or  mon-acid  phenols ;  those  containing 
two  hydroxyls,  or  di-add  phenols ;  those  containing  three  hy- 
droxyls,  or  tri-acid  phenols,  etc.  ...  Some  of  these  are  familiar 
substances. 

MON-ACID  PHENOLS. 

Phenol,  carbolic  acid,  C6H6O(=  C6H5OH).  —  Phenol  is 
found  in  nature  in  small  quantities  in  the  urine.  It  is  formed 
by  the  distillation  of  wood,  coal,  and  bones.  Hence,  it  is  a 
constituent  of  coal  tar,  and  from  this  it  is  prepared.  For  this 
purpose  the  heavy  oil  (see  p.  231)  is  treated  with  an  alkali 
which  dissolves  the  phenol.  From  the  solution  it  is  precipitated 
by  hydrochloric  acid.  It  is  purified  by  distillation. 

Phenol  may  also  be  made  by  converting  nitro-benzene  into 
aniline ;  then  into  diazo-benzene,  and  boiling  this  with  water 
(see  Exp.  62  (&))  ;  and  by  melting  benzene-sulphonic  acid 
with  potassium  hydroxide. 


270  DERIVATIVES    OF   THE   BENZENE   SERIES. 

Experiment  66.  In  a  silver  (or  iron)  crucible,  or  evaporating 
dish,  melt  40s  to  50»  potassium  hydroxide,  after  adding  a  few  cubic 
centimetres  of  water.  Now  add  gradually  10?  finely-powdered  potas- 
sium benzene-sulphonate,  obtained  in  Exp.  63,  stirring  constantly  with 
a  silver  (or  iron)  spatula.  Do  not  heat  to  a  very  high  temperature. 
After  the  mass  has  been  kept  in  a  state  of  fusion  for  one-quarter  to 
one-half  an  hour,  let  it  cool.  Dissolve  in  200CC  to  250CC  water,  and 
acidify  with  hydrochloric  acid.  Notice  the  odor  of  the  gases  given 
off.  What  gas  do  you  detect?  When  the  liquid  has  cooled  down, 
extract  with  ether  in  a  glass-stoppered  cylinder.  From  the  ether 
extract  distil  the  ether  on  a  water-bath.  The  residue  is  impure  phenol, 
which  may  be  detected  by  the  following  reactions,  for  which  a  solution 
in  water  should  be  prepared :  — 

(a)  A  few  drops  of  ferric  chloride  solution  gives  a  beautiful  violet 
color. 

(6)  Add  one-fourth  volume  of  ammonia,  and  then  a  few  drops  of 
a  dilute  solution  of  bleaching  powder.  A  blue  color  is  produced. 

(c)  Bromine  water  gives  a  yellowish-white  precipitate  of  tri-brom- 
phenol. 

The  reaction  which  takes  place  in  melting  potassium  hydrox- 
ide and  potassium  benzene-sulphonate  together  is  represented 
by  the  equation,  — 

C6H5.S03K  +  KOH  =  CGH5.OH  +  K2SO3. 

It  effects  the  replacement  of  the  sulpho  group,  SO3H,  by 
hydroxyl. 

Phenol,  when  pure,  crystallizes  in  beautiful  colorless  rhombic 
needles.  The  presence  of  a  little  water  prevents  it  from  solidi- 
fying. It  has  a  peculiar,  penetrating  odor ;  boils  at  180°  ;  is 
difficultly  soluble  in  water  (1  part  in  15  parts  water  at  ordinary 
temperature) ;  mixes  with  alcohol  and  ether  in  all  proportions ; 
and  is  poisonous. 

Phenol  forms  compounds  with  several  metals.  Among  these 
may  be  mentioned  the  following  :  — 

Potassium  phenolate,  C6H5  .OK,  made  by  dissolving  potassium 
in  phenol,  and  by  treating  phenol  with  caustic  potash. 

Barium  phenolate,  (C6H5O)2Ba  -j-  2  H2O,  made  by  dissolving 
phenol  in  baryta  water. 


PHENYL   ACETATE.  271 

Lead  oxide  phenol,  C6H6O.PbO,  made  by  dissolving  lead 
oxide  in  phenol. 

It  also  forms  ethers,  of  which  the  methyl  and  diphenyl  ethers 
may  serve  as  examples  :  — 


Methyl-phenyl  ether,  C7H8o(-  ^5>  O\  —  This    sub- 

stance, also  called  anisol,  is  obtained  from  anisic  acid  and  from 
oil  of  winter-green  by  boiling  with  baryta  water.  It  is  made 
also  by  treating  potassium  phenolate,  C6H5OK,  with  methyl 
iodide  :  — 

C6H5OK  +  CH3I  =  ^7>0  +  KI. 

Crl3 

It  is  a  liquid  of  a  pleasant  odor. 

NOTE  FOR  STUDENT.  —  Compare  this  substance  with  ordinary  ether. 
What  method  analogous  to  that  above  mentioned  may  be  used  in  the 
preparation  of  ordinary  ether? 


Diphenyl   ether,    O1^10of=  ^5  >  O  \  —  This    bears   to 

V     O6H5          / 

phenol  the  same  relation  that  ordinary  ether  bears  to  alcohol. 

With  acids,  phenol,  like  the  alcohols,  yields  ethereal  salts  in 
which  the  phenyl  group,  C6H5,  takes  the  place  of  a  metal. 
Among  the  compounds  of  this  class  which  phenol  forms  with 
organic  acids,  the  following  may  be  mentioned  :  — 

Phenyl  acetate,  C8H«O2(=  CH3.CO2.C6H5).—  This  is  formed 
by  treating  phenol  with  acetyl  chloride. 

NOTE  FOR  STUDENT.  —  What  use  is  acetyl  chloride  put  to  as  a  re- 
agent in  organic  chemistry?  Explain  its  use.  What  conclusion  may 
be  drawn  from  the  fact  that  acetyl  chloride  acts  upon  phenol,  replacing 
one  hydrogen  by  acetyl,  C2H30? 

Substitution-products  of  phenol.  Phenol  is  very  susceptible 
to  the  action  of  various  reagents,  and  a  large  number  of  substi- 
tution-products have  been  made  from  it. 

The  ease  with  which  bromine  acts  upon  it  was  illustrated  in 


272 


DERIVATIVES    OF   THE   BENZENE    SERIES. 


Exp.  66  (c).     It  was  shown  that,  by  the  addition  of  bromine 

water  to  the  water  solution  of  phenol,  tri-brom -phenol  is  formed. 

Dilute  nitric  acid  acts  upon  phenol,  yielding  two  moD.o-n.itro- 

phenols,  C6H4<       2,  one  of  which  has  been  shown  to  belong  to 
(  OH 

the  ortho  series,  the  other  to  the  para  series. 

Experiment  67.  Add  20s  phenol  to  a  mixture  of  80CC  water  and 
40CC  ordinary  concentrated  nitric  acid  (sp.  gr.  1.34).  Stir,  and,  after  a 
time,  pour  off  the  dilute  acid  from  the  oil.  Wash  with  water,  and  then 
put  it  into  a  flask,  with  about  a  litre  of  water,  arranged  as  shown  in 
Tig.  15.  Flask  A  holds  nothing  but  water;  while  the  oil,  together  with 


A- 


Fig.  15. 

water,  are  in  B.  From  A  a  current  of  steam  is  passed  into  B,  which 
is  heated  by  means  of  a  lamp.  Yellow  crystals  pass  over  and  appear 
in  the  receiver,  while  a  non-volatile  substance  remains  behind  in  flask 
B.  The  volatile  substance  is  ortho-nitro-phenol ;  the  non-volatile  is 
para-nitro-phenol. 

Tri-nitro-phenol,  picric  acid,  C6H3N3O7(  =  C6H2  f 


This  is  formed  very  easily  by  the  action  of  strong  nitric  acid  on 
phenol. 

Experiment   68.    Dissolve  108  to  15g  phenol  in  weak  nitric  acid, 
and  to  this  solution  slowly  add  some  strong  nitric  acid.     Afterward 


PHENYL   MEKCAPTAN.  273 

dilute  with  water;  filter  off  the  picric  acid,  and  wash.  Dissolve 
in  dilute  potassium  carbonate  solution,  and  evaporate  to  crystalliza- 
tion. 

.  Picric  acid  forms  yellow  crystals,  has  a  very  bitter  taste, 
is  poisonous,  decomposes  with  explosion  when  heated  rapidly. 
It  dyes  wool  and  silk  yellow. 

NOTE  FOR  STUDENT.  —  Is  there  any  analogy  between  tri-nitro- 
phenol  and  tri-nitro-glycerin?  What  is  the  essential  difference  be- 
tween them? 

One  of  the  most  interesting  properties  of  tri-nitro-phenol  is 
its  power  to  form  salts.  It  acts  like  a  strong  acid.  It  will 
thus  be  seen,  that,  while  the  substance  C6H5  .OH  has  only  very 
slight  acid  properties,  the  same  substance,  with  three  of  its 
hydrogens  replaced  by  nitro  groups,  C6H2(NO2)3.OH,  has 
strong  acid  properties.  In  the  salts,  which  have  the  general 
formula  C6H2(NO2)3.-OM,  the  metals  replace  the  hydrogen  of 
the  hydroxyl.  Among  them  may  be  mentioned  the  potassium 
salt  which  was  obtained  in  Exp.  68  ;  this  explodes  when  heated 
and  when  struck.  Ammonium  picrate,  C6H2(NO2)3.ONH4,  is 
used  as  a  constituent  of  explosives. 


Phenyl  mercaptan,        -i  _ 

^C6HgS{=C(ft.8H  .-— This  bears 

Phenyl  hydrosulphide,  I 

the  same  relation  to  phenol  that  mercaptan  bears  to  alcohol. 
It  may  be  made  by  reducing  benzene-sulphonic  acid.  This 
reduction  is  effected  by  first  making  the  sulphon-chloride, 
C6H5.SO2C1,  (Exp.  64),  and  then  treating  this  with  nascent 
hydrogen. 

NOTE  FOR  STUDENT.  —  What  is  the  effect  of  oxidizing  the  mercap- 
tans? 

It  may  be  made,  also,  by  treating  phenol  with  phosphorus 
pentasulphide,  the  effect  of  this  reagent  being  to  replace  oxy- 
gen by  sulphur. 


274  DERIVATIVES    OF    THE   BENZENE   SERIES. 

NOTE  FOR  STUDENT.  —  What  analogy  is  there  between  the  action  of 
phosphorus  pentachloride  and  of  phosphorus  peutasulphide  on  com- 
pounds containing  oxygen? 

Pheuyl  mercaptan  is  a  liquid,  with  a  very  disagreeable 
odor.  With  mercuric  oxide  it  forms  a  crystallized  com- 
pound, (C6H5S)2Hg. 


Cresols,  C7H8O  =  C6H4  <  ^-J  .  —  There  are  three  cresols, 


or  hydroxyl  derivatives  of  toluene,  of  the  formula  C6H4  <       3. 

OH 

They  are  all  found  in  coal  tar,  and  the  tars  from  pine  and  beech 
wood.  When  mixed  together,  it  is  difficult  to  separate  them. 
To  obtain  them  in  pure  condition,  it  is  therefore  best  to  make 
them  from  the  three  toluidines,  or  from  the  three  sulphonic  acids 
of  toluene. 

NOTE  FOR  STUDENT.  —  Give  the  equations  representing  the  reactions 
involved  in  passing  from  the  three  toluidiues  to  the  cresols,  and  from 
the  three  toluene-sulphonic  acids  to  the  cresols. 

The  cresols  resemble  phenol  very  closety. 

Creosote  is  a  mixture  of  chemical  compounds  contained  in 
wood  tar.  It  contains  the  cresols.  Coal-tar  creosote  consists 
largely  of  phenol. 

CH3 
Thymol,  propyl-meta-cresol,  C10HUO  =  C(;H3    OH  («0 


This  phenol  is  contained  in  oil  of  thyme,  together  with  cymene. 
It  forms  large  monoclinic  crystals,  which  melt  at  50°.  It  has  a 
pleasant  odor,  like  that  of  the  oil  of  thyme.  Treated  with  phos- 

1  Formulas  of  this  kind  serve  very  well  to  indicate  the  relations  of  the  groups  and 
atoms  contained  in  benzene  derivatives.  This  one,  for  example,  indicates  that  the 
hydroxyl  is  in  the  meta  position  (m)  to  methyl;  while  the  propyl  is  in  the  para 
position  to  methyl  (/>)'.  For  bi-substitution  products,  such  formulas  may  also 

be    used.        Thus,    the    three    toluidiues    may    be    represented    by    CCH4  <       3 
*       ,  and    CHCH3 


DI-ACID    PHENOLS.  275 

phorus  pentoxide,  it  yields  meta-cresol ;  while,  when  treated 
with  phosphorus'  pentasulphide,  it  yields  cymene.  These  two 
reactions  indicate  that  the  groups  contained  in  thymol  bear  to 
each  other  the  relations  indicated  by  the  formula  given  above. 
It  is  one  of  the  two  theoretically  possible  hydroxyl  derivatives 
of  cymene.  The  other  one,  carvacrol,  has  the  hydroxyl  in  the 
ortho  position  relatively  to  methyl.  It  has  been  made  from 
the  corresponding  cymene-sulphonic  acid ;  is  found  in  nature 
in  the  ethereal  oil  of  Origanum  hirtum  ;  and  may  be  made  from 
carvol,  or  the  oil  of  caraway. 

DI-ACID  PHENOLS. 
The    three     theoretically    possible     di-hydroxyl     benzenes, 

OTT 

C6H4<OH,   are   all  well   known. 

Pyrocatechin,  \CHof=CH  <  OH 

Ortho-di-hydroxy-benzene,  J  \  OH(o) 

This  substance  is  a  frequent  product  of  the  dry  distillation  of 
natural  substances,  —  as  of  catechu,  morintannic  acid,  etc., — 
and  of  the  melting  of  resins  with  caustic  potash.  It  may  be 
made  by  melting  ortho-iodo-phenol  or  ortho-phenol-sulphonic 
acid  with  caustic  potash.  It  forms  crystals,  which  melt  at 
104°.  It  is  easily  soluble  in  water,  alcohol,  and  ether. 

The  dilute  solution  in  water  gives  with  ferric  chloride  a 
dark-green  color,  which  becomes  violet  on  the  addition  of  a 
little  sodium  carbonate. 

Resorcin,  *  C  H  O  f-  C  H  <"  ^^ 

Meta-di-hydroxy-benzene,  ?  \  OH(m) 

Resorcin  is  formed  by  the  melting  of  a  number  of  resins  with 
caustic  potash,  as  of  galbanum,  sagapennm,  asafoetida,  etc. 
It  is  made,  also,  by  melting  meta-iodo-phenol  or  meta-benzene- 
disulphonic  acid  with  caustic  potash. 

It  crystallizes  from  water,  usually  in  thick  rhombic  prisms, 
Melting-point,  110°. 


276  DERIVATIVES    OF   THE   BENZENE   SERIES. 

With  ferric  chloride,  the  water  solution  gives  a  dark  purple 
color.  Heated  for  a  few  minutes  with  phthalic  acid  in  a  test- 
tube,  a  yellowish-red  mass  is  formed.  When  this  is  added 
to  dilute  caustic  soda,  a  wonderfully  fluorescent  solution  is 
obtained.  The  explanation  of  this  reaction  will  be  given 
under  the  head  of  Tri-phenyl-me  thane,  when  the  phthaleins 
will  be  considered. 

Resorcin  is  used  largely  in  the  manufacture  of  certain  dyes, 
and  is  therefore  manufactured  on  the  large  scale. 


Tri-nitro-resorcin,  i/ 

d,      ,     .  .  ,  Y  v-'G-tis-N  a^-M  —  O6±±     //-VTT\ 

Styphmc    acid,  V  I  (OH)2 

compound  is  formed  by  the  action  of  nitric  acid  on  resorcin, 
and  on  those  resins  which  give  resorcin  when  treated  with 
caustic  potash.  It  closely  resembles  picric  acid.  Heated 
with  bromine  and  acetic  acid,  it  yields  the  substance  known 
as  brompicrin,  which  has  the  formula  C(NO2)Br3. 


Hydroquinone, 

Para-di-hydroxy-benzene,  /  \~         l      OH(p) 

H3'droquinoue  is  formed  by  the  dry  distillation  of  quinic  acid, 
by  reduction  of  quiuone  (which  see),  by  the  action  of  chromic 
acid  on  aniline,  by  melting  para-iodo-phenol,  etc. 

It  is  a  crystallized  substance  which   melts  at  169°  ;    easily 
soluble  in  alcohol,  ether,  and  hot  water. 

Oxidizing  agents,  such  as  ferric  chloride,  chlorine,  etc.,  con- 
vert it  into  quinone. 


It  would  lead  us  too  far  to  consider  here  the  reactions  which 
bave  been  made  use  of  for  the  purpose  of  determining  to  which 
series  each  of  the  three  di-hydroxy-benzenes  belongs.  The 
principle  involved,  however,  is  simple.  Either  these  substances 
must  be  converted,  directly  or  indirectly,  into  others,  in  regard 
to  the  relation  of  whose  groups  we  have  evidence  ;  or  sub- 
stances, the  relation  of  whose  groups  is  known,  must  be  con- 


TKI-ACID   PHENOLS.  277 

verted  into  the  di-hydroxy -benzenes.  The  reactions  made  use 
of  for  effecting  the  conversions  are  mainly  those  which  have 
already  been  considered;  viz.,  the  formation  of  amido  com- 
pounds from  nitro  compounds  by  reduction ;  the  formation  of 
diazo  compounds  from  amido  compounds ;  the  formation  of 
(1)  hydroxyl  derivatives,  (2)  chlorine,  bromine,  or  iodine  de- 
rivatives, from  the  diazo  compounds ;  and  the  formation  of 
hydroxyl  derivatives  from  sulphonic  acids. 


Orcin,  i  /-«  TT  r\  /  _  o  -cr  )  ^-"-s     ^   There 


Di-hydroxy-  toluene, 
are  three  dye-stuffs,  known  as  archil,  cudbear,  and  litmus,  which 
are  made  from  different  lichens  by  exposing  them  in  powdered 
condition  in  ammoniacal  solution  to  the  action  of  air.  They 
are  treated  with  decomposing  urine,  from  which  the  ammonia 
is  obtained.  Archil  contains  a  substance  called  orcein,  which 
may  be  made  from  orcin  by  treating  it  with  ammonia.  Orcin 
is  contained  in  several  lichens.  It  is  formed,  also,  by  melting 
aloes  with  caustic  potash,  and  by  melting  chlor-toluene-sulpho- 
nic  acid  with  caustic  potash.  The  last  reaction  shows  that 
orcin  is  a  di-hydroxy-toluene. 

Orcin  crystallizes  in  large,  colorless,  monoclinic  prisms. 
Turns  red  in  the  air.  Ferric  chloride  turns  the  aqueous 
solution  deep  violet. 

Treated  with  ammonia  in  moist  air,  it  is  converted  into 
orcein,  (^R^NO^,  a  substance  which  dissolves  in  alkalies, 
forming  beautiful  red  solutions. 

Orcin  is  manufactured  on  the  large  scale,  and  then  con- 
verted into  orcein,  which  is  used  as  a  dye. 

TRI-ACID  PHENOLS. 
Pyroifallol,     pyrogallic    acid, 

m     .    ,  ,  , 

Tri-hydroxy-benzene, 
Pyrogallic  acid  is  formed  by  dry  distillation  of  gallic  acid,  the 


278  DERIVATIVES   OF   THE   BENZENE   SERIES. 

reaction  being  analogous  to  that  by  which  benzene  is  produced 
by  distillation  of  benzoic  acid  :  — 

C6H5.C02H      =  CGH6  +  C02; 

Benzoic  acid.  Benzene. 


C6H2{  3  =  CeHs(OH)3  4-  C02. 

I  CO2H  Pyrogallol. 

Gallic  acid. 

It  is  formed  also  when  one  of  the  chlor-phenol-sulphonic  acids 
is  melted  with  caustic  potash  :  — 

(OH  r  OH 

C&H3  1  Cl        +  *°:  *  =  C6H3  }  OH  4-  KC1  4  K*SO3. 

(S03K  (OH 

Potassium  chlor-phenol-  Pyrogallol. 

sulphonate. 

It  crystallizes  in  laminae  or  needles  ;  melts  at  115°  ;  is  easily 
soluble  in  water,  ether,  and  alcohol.  In  alkaline  solution  it 
absorbs  oxygen  rapidly  and  becomes  brown.  On  account  of 
this  power  to  absorb  oxygen  it  is  used  in  gas  analysis.  It  is 
poisonous. 

With  a  solution  containing  a  ferrous  and  a  ferric  salt  it  gives 
a  blue  color. 

Most  of  the  phenols  give  color  reactions  with  feme  chloride, 
and  most  of  them  change  color  in  the  air.  These  changes  in 
color  are  undoubtedly  due  to  the  action  of  oxygen  upon  them. 
Towards  oxidizing  agents  the}7  are  all  unstable,  most  of  them 
breaking  down  readily  and  yielding  as  the  chief  product  of 
oxidation,  carbon  dioxide.  In  general,  the  larger  the  number 
of  hydroxyl  groups  contained  in  a  phenol  the  less  stable  it  is. 
We  shall  see  that  these  same  statements  hold  good  for  the 
hydroxy-acids  of  the  benzene  group,  of  which  gallic  acid  and 
salicylic  acid  are  examples. 

ALCOHOLS  OF  THE  BENZENE  SERIES. 

The  phenols  are  those  hydroxyl  derivatives  of  the  benzene 
hydrocarbons,  which  contain  the  hydroxyl  in  the  place  of  one 
or  more  of  the  six  benzene  hj'drogens.  But  just  as  there  are 


BENZYL   ALCOHOL.  279 

two  classes  of  halogen  substitution-products  of  toluene,  in  one 
of  which  the  substitution  has  taken  place  in  the  benzene 
residue,  and  in  the  other  in  the  marsh-gas  residue,  as  indicated 
in  the  two  formulas,  — 

C6H4C1.CH3      and      C6H5.CH2C1, 

so,  also,  there  are  two  classes  of  hydroxyl  derivatives:  (1)  the 
phenols,  and  (2)  those  in  which  the  hydroxyl  is  in  the  marsh- 
gas  residue.  The  simplest  example  of  the  second  class  corre- 
sponds to  the  formula,  C6H5.CH2.OH.  It  is  isomeric  with  the 
cresols,  C6H4.OH.CH3,  and  has  entirely  different  properties. 
While  the  cresols  are  the  true  homologues  of  phenol,  the  new 
substance  is  really  methyl  alcohol  in  which  one  of  the  hydrogens 
of  the  methyl  has  been  replaced  by  phenyl,  C6H5.  It  may 


be  represented  by  the  formula,  C  ,  when  its  analogy  to 


TT 

TT    ,  is  at  once  apparent. 
H 

OH 

Benzyl  alcohol,  C7H8O(=  C6H5.CH2OH).  —  Benzyl  alcohol 
or  pheuyl  carbinol  is  found  in  nature  in  the  balsams  of  Peru 
and  Tolu,  and  in  storax.  In  these  substances  it  is,  for  the 
most  part,  in  combination  with  beuzoic  or  cinnamic  acid.  It  is 
made  by  treating  the  oil  of  bitter  almonds,  which  is  the  corre- 
sponding aldehyde,  with  nascent  hydrogen  :  — 

C6H5.CHO  +  H2  =  C6H5.CH2.OH. 

Oil  of  bitter  almonds.  Benzyl  alcohol. 

It  is  also  made  by  replacing  the  chlorine  in  benzyl  chloride, 
C6H5.CH2C1,  by  hydroxyl,  just  as  methyl  alcohol  is  made  from 
methyl  chloride  by  a  similar  replacement.  In  the  case  of 
benzyl  chloride  it  may  be  effected  even  by  boiling  for  a  long 
time  with  water  :  — 

C6H5.CH2C1  +  H20  =  C6H5,CH2OH  +  HC1. 


280  DERIVATIVES    OF   THE   BENZENE   SERIES. 

Benzyl  alcohol  is  a  liquid  with  a  pleasant  odor.  It  boils  at 
206.5°. 

NOTE  FOR  STUDENT.  —  Notice  the  great  difference  between  the  boil- 
ing-point of  methyl  alcohol  and  phenyl-methyl  alcohol. 

Oxidizing  agents  convert  the  alcohol,  first,  into  the  oil  of 
bitter  almonds  or  benzoic  aldehyde,  and  finally  into  benzoic 
acid.  The  relations  between  the  three  substances  are  like 
those  between  any  primary  alcohol  and  the  corresponding  alde- 
hyde and  acid,  as  shown  by  the  formulas,  — 

C7H80,  C7H60,  C7H(J02, 

or  C6H5  .CH2OH  ;    or  C6H5  .CHO  ;         or  C6H5  .CO2H. 

Benzyl  alcohol.  Benzoic  aldehyde.  Beuzoic  acid. 

Hydriodic  acid  converts  benzyl  alcohol  into  toluene  :  — 
C6H5.CH2OH  +  2  HI  =  CGH5.CH3  +  H2O  +  2  I. 

Benzyl  alcohol  conducts  itself,  in  most  respects,  like  the 
primary  alcohols  of  the  methyl  alcohol  series.  A  large  number 
of  its  derivatives  have  been  made  and  studied.  Among  them 
are  ethereal  salts,  of  which  benzyl  acetate,  CH3.CO.OC7H7,  and 
benzyl  nitrate,  NO2.OC7H7,  may  serve  as  examples;  ethers,  of 
which  the  methyl  ether,  C6H5.CH2.O.CH3,  and  the  phenyl  ether, 
C6H5.CH2.OC6H5,  are  good  examples  ;  and  substitution-products, 
of  which  chlor-benzyl  alcohol,  C6H4C1.CH2OH,  and  nitro-bemyl 
alcohol,  C6H4(NO2).CH2OH,  are  examples. 

These  substitution-products  are  not  made  by  direct  treatment 
of  the  alcohol  with  the  substituting  agents,  but  by  starting  from 
the  corresponding  substituted  toluene.  Thus,  chlor-benzyl 
alcohol  is  made  from  chlor- toluene,  CGH4C1.CH3,  by  first  con- 
verting this  into  chlor-benzyl  chloride,  C6H4C1.CH2C1,  and  then 
replacing  the  chlorine  of  the  group  CH2C1  by  hydroxyl.  By 
oxidation  the  substituted  benzyl  alcohols  yield  the  correspond- 
ing substituted  benzoic  acids  :  — 

C6H4C1.CH2OH        +  02  =  C6H4C1.C02H       +  H2O. 

Chlor-benzoic  acid. 

C6H4(N02).CH2OH  +  O2  =  C6H4(N02)C02H  +  H2O. 

Nitro-benzoic  acid. 


ALDEHYDES    OF   THE   BENZENE    SERIES.  281 

Very  few  of  the  alcohols  analogous  to  benzyl  alcohol  have 
been  prepared.  Plainly,  the  homologues  may  be  of  two  kinds  : 

1.  Those  which  are  phenyl  derivatives  of  the  alcohols  of  the 
methyl    alcohol   series.      Of   this    class,    phenyl-ethyl  alcohol, 
C6H5.CH2.CH2OH,  the  isomeric  substance  C6H5.CH.  OH.  CH3, 
and   phenyl-propyl     alcohol,    C6H5.CH2.CH2.CH2OH,   are  ex- 
amples.     Phenyl-propyl    alcohol     is    of    special    interest   on 
account   of  its    connection   with   cinnamic    acid    (which    see), 
which  has  come  into  prominence  since  it  has  been  shown  to  be 
closely  related  to  the  interesting  substances  of  the  indigo  group. 
It  occurs  in  storax  in  the  form  of  an  ethereal  salt,  which  will 
be  spoken  of  more  fully  under  the  head  of  Cinnamic  Acid. 

2.  Those  which  are  derivatives  of  xylene,  mesitylene,  etc., 
in  the  same  sense  as  benzyl  alcohol  is  a  derivative  of  toluene. 
The  following  belong  to  this  class  :  — 

Tolyl  carbinol      ....     C6H4< 

and          Cuminyl  alcohol  .     .     .     .     C6H4<CH2°H, 

C8H7(_p) 

which  is  made  from  cuminol,  an  aldehyde  found  in  the  oil  of 
caraway. 

ALDEHYDES  OF  THE  BENZENE  SERIES. 

The  aldehydes  of  this  group  are  closely  related  to  the  alco- 
hols just  considered.  The  simplest  one  is  the  oil  of  bitter 
almonds,  or  benzoic  aldehyde,  C7H6O. 

Oil  of  bitter  almonds,        __          „  __  ^ITTANN 

.  —  Thissub- 


Benzoic  aldehyde, 
stance  occurs  in  combination  in  amygdalin,  which  is  found  in 
bitter  almonds,  laurel  leaves,  cherry  kernels,  etc.  Amygdalin 
belongs  to  the  class  of  bodies  known  as  gfaco  sides,  which  break 
up  into  a  glucose  and  other  substances.  Amygdalin  itself, 
under  the  influence  of  emulsin,  which  occurs  with  it  in  the 


282  DERIVATIVES    OF   THE   BENZENE   SERIES. 

plants,  breaks  up  into  benzole  aldehyde,  hydrocyanic  acid,  and 
dextrose  :  — 

C20H27NOn  +  2  H20  =  C7HG0  +  CNH  +  2  C6H12O6. 

Amygdalin.  Benzole  aldehyde.  Dextrose. 

Benzole  aldehyde  may  be  made  : 
1  .  By  oxidizing  benzyl  alcohol  :  — 

C6H5.CH2OH  +  O  =  C6H5.CHO  +  H2O. 

2.  By  distilling  a  mixture  of  calcium  benzoate  and  calcium 
formate  :  — 


3.  By  treating  benzoyl  chloride,  the  chloride  of  benzoic  acid, 
with  nascent  hydrogen  :  — 

C6H5.COC1  +  H2  =  C6H5.CHO  +  HC1. 

4.  By  treating  benzal  chloride  with  water  or  mercuric  oxide  :  — 

C6H6.CHC12  +  H2O  =  C6H5.CHO  +  2  HC1. 

NOTE  FOR  STUDENT.  —  Refer  to  the  general  methods  for  the  prepara- 
tion of  aldehydes.  Which  of  the  above  reactions  are  used  for  the 
preparation  of  aldehydes  in  general?  Which  of  the  reactions  throw 
light  upon  the  nature  of  aldehydes,  and  their  relation  to  alcohols? 

Benzoic  aldehyde  is  prepared  either  from  bitter  almonds, 
which  yield  about  1.5  to  2  per  cent;  or  from  benzal  chloride, 
according  to  reaction  4,  above  given.  The  latter  method  is 
employed  in  the  artificial  preparation  of  indigo. 

Benzoic  aldehyde  is  a  liquid  having  a  pleasant  characteristic 
odor.  It  boils  at  179°;  is  difficultly  soluble  in  water;  is  not 
poisonous. 

It  unites  with  oxygen  to  form  benzoic  acid  ;  with  hydrogen 
to  form  benzyl  alcohol  ;  with  hydrogen  sulphide,  ammonia, 
ammonium  sulphide,  alcohols,  acids,  anhydrides,  and  ketones. 
In  short,  its  powers  of  combination  with  other  substances  are 


MONOBASIC   ACIDS,    CnH2n_8O2.  283 

almost  unlimited.     Hence,  a  very  large  number  of  derivatives 
are  known. 

f'TTO 

= 


This  aldehyde  occurs  in  oil  of  caraway,  from  which  it  is  made. 
It  is  a  liquid  with  .the  odor  of  the  oil  of  caraway.  Its  reactions 
are  like  those  of  benzoic  aldehyde. 

ACIDS  OF  THE  BENZENE  SERIES. 

The  simplest  of  these  acids  has  been  referred  to  repeatedly. 
It  is  benzoic  acid,  which  bears  to  benzene  the  same  relation 
that  acetic  acid  bears  to  marsh  gas.  It  is  the  carboxyl  deriva- 
tive of  benzene.  The  homologous  acids  are  the  carboxyl 
derivatives  of  the  homologous  hydrocarbons.  We  shall  find 
mono-basic,  di-basic,  tri-basic,  and  even  hexa-basic  acids, 
though  the  number  of  acids  actually  known  is  small. 

MONOBASIC  ACIDS,  CnH2n_8O2. 

Benzoic  acid,  CTHCO2(=  CCH5.CO2H). — Benzoic  acid  occurs 
in  gum  benzoin,  in  the  balsams  of  Peru  and  Tolu,  and  in 
combination  with  amido-acetic  acid  or  glycin  in  the  urine  of 
herbivorous  animals.  It  ma3~  be  made  in  many  ways,  the  most 
important  of  which  are  stated  below  :  — 

1 .  By  oxidation  of  benzyl  alcohol  or  any  alcohol  which  is  a 
phenyl  derivative  of  an  alcohol  of  the  methyl  alcohol  series. 
The  common  condition  in  all  these  alcohols  is  the  presence  of 
the  difficultly  oxidizable  residue,  C6H5,  in  combination  with  an 
easily  oxidizable  residue  of  an  alcohol  of  the  marsh-gas  series  :  — 

C6H5  .CH2OH  gives     C6H5  .CO,H  ; 

C6H5  .CII2  .CH,OH  "        C6H5  .CO2H  ; 

CGH5.CH2.CH2,CH2OH       "        C6H5.CO2H,  etc. 


284  DERIVATIVES    OF   THE   BENZENE   SERIES. 

2.  By  oxidation  of  benzoic  aldehyde,  and  the  aldehydes  of 
the  other  alcohols  referred  to  in  the  preceding  paragraph. 

3.  By  oxidation  of  all  benzene  hydrocarbons  which  contain 
but  one  residue  of  the  marsh-gas  series.    Attention  has  already 
been  called  to  this  fact  (see  p.  246). 

4.  By  treating  cyan-benzene  (phenyl  cyanide,  benzo-nitrile) 
with  a  caustic  alkali  (see  Exp.  65,  p.  267)  :  — 

C6H5CN  +  KOH  +  H20  =  C6H5.CO2K 


5.  By  treating  benzene  with  carbonyl  chloride  in  the  presence 
of  aluminium  chloride  :  — 

C6H6  +  COC12          =  C6H5.COC1   +  HC1; 
C6H5.COC1  +  H20  =  C6H5.C02H  +  HC1. 

A  reaction  similar  to  this  is  of  extensive  application  in  the 
preparation  of  some  hydrocarbons.  It  will  be  spoken  of  more 
fully  under  the  head  of  Tri-phenyl-methane. 

6.  By  treating  benzene  with  carbon  dioxide  in  the  presence 
of  aluminium  chloride  :  — 

C6H6+  C02=  C6H5.CO2H. 

This  and  the  preceding  methods  are  of  special  interest  from  the 
scientific  stand-point,  for  the  reason  that  they  clearly  show  the 
relation  which  exists  between  benzoic  acid,  on  the  one  hand, 
and  benzene  and  carbonic  acid,  on  the  other. 

NOTE  FOR  STUDENT.  —  Which  of  the  methods  above  given  are  of 
general  application  for  the  preparation  of  the  acids  of  carbon? 

Beuzoic  acid  is  prepared  on  the  large  scale  :  (1)  from  gum 
benzoin  by  sublimation  ;  (2)  from  the  urine  of  horses  and 
cows  by  treating  the  hippuric  acid  with  hydrochloric  acid  ; 
(3)  from  toluene,  best,  by  converting  it  into  benzyl  chloride, 
and  oxidizing  this  with  dilute  nitric  acid. 

Experiment  69.  If  the  material  is  obtainable,  evaporate  a  quantity 
of  the  urine  of  horses  or  cows  to  about  one-half  or  one-third  its  vol- 


BENZOIC   ACID.  285 

umc.  Add  hydrochloric  acid.  On  cooling,  hippuric  acid  will  be 
deposited.  Eecrystallize  this  several  times  from  dilute  nitric  acid. 
Boil  the  hippuric  acid  for  about  a  quarter  of  an  hour  with  ordinary 
concentrated  hydrochloric  acid.  By  this  means  the  hippuric  acid  is 
decomposed,  yielding  glycin  (amido-acetic  acid)  and  benzole  acid :  — 

C9H9N03  +  H20  =  C7H602  +  CH2<™2 

Hippuric  acid.  Benzoic  acid.  ^Ujtl 

Glycin. 

Benzoic  acid  forms  lustrous  laminae  or  needles,  which  melt 
at  121°. 

Experiment  70.  Compare  the  melting-points  of  the  two  speci- 
mens of  benzole  acid  which  haVe  been  made:  (1)  from  phenyl 
cyanide  (Exp.  65),  and  (2)  from  urine.  If  they  are  not  the  same, 
recrystallize  the  specimens  from  water  until  the  melting-points  are 
not  changed  by  further  crystallization.  Those  specimens  which  are 
least  pure  may  be  purified  by  recrystallizing  them  from  dilute  nitric 
acid. 

The  acid  is  comparatively  easily  soluble  in  hot  water,  but 
difficultly  soluble  in  cold  water.  It  is  volatile  with  water 
vapor. 

Experiment  71.  Put  some  in  a  one-litre  flask,  with  about  700CC  to 
800CC  water.  Connect  with  a  condenser,  and  boil  down  to  about  200CC. 
Neutralize  the  distillate  with  ammonia,  and  evaporate  down  to  a  small 
volume.  Acidify,  when  benzole  acid  will  be  thrown  down. 

Its  vapor  acts  upon  the  mucous  membrane  of  the  respiratory 
passages,  producing  coughing. 
It  sublimes  very  easily. 

Experiment  72.  Put  some  dry  benzoic  acid  in  a  small,  dry  crystal- 
lizing dish,  and  put  the  dish  in  a  sand-bath.  Over  the  mouth  of  the 
dish  put  a  paper  cone  made  from  filter-paper,  arranged  as  shown  in 
Fig.  16.  Heat  with  a  small  flame.  The  benzoic  acid  will  be  deposited 
on  the  paper  in  beautiful  lustrous  needles. 

Or  another  form  of  apparatus,  which  is  useful  for  subliming  small 
quantities  of  substance,  consists,  essentially,  of  two  watch-glasses 
which  are  of  exactly  the  same  size.  The  edges  of  the  glasses  are 
ground  to  secure  a  good  joint  when  they  are  brought  together.  In 


286 


DERIVATIVES    OF   THE   BENZENE   SERIES. 


using  this  apparatus,  put  the  substance  to  be  sublimed  in  one  of  the 
glasses ;  stretch  a  round  piece  of  filter-paper  over  it,  and  then  place 
the  other  glass  upon  it.  Clamp  the  glasses  together  by  means  of  a 
thin  brass  clamp.  Now  put  the  glasses  on  a  sand-bath,  and  warm 


1     liiiiilliil    m 


Fig.  16. 

gently,  when  the  substance  will  slowly  pass  through  the  paper  and 
appear  in  crystals  in  the  upper  watch-glass.  It  is  well  to  keep  a  small 
pad  of  moist  filter-paper  on  the  upper  glass  during  the  operation. 

When  heated  with  lime,  benzoic  acid  breaks  up  into  benzene 
and  carbon  dioxide  (see  Exp.  55)  :  — 

C7H6O2  =  C6H6  -f-  CO2. 

With  sodium  amalgam,  it  yields  benzyl  alcohol  and  other  reduc- 
tion-products. With  hydriodic  acid,  it  yields  toluene,  and  then 
hydrogen  addition- products  of  toluene. 

A  great  mau}r  derivatives  of  benzoic  acid  are  known. 


SUBSTITUTION-PRODUCTS    OF   BENZOIC   ACID.         287 

Nearly  all  its  salts  are  soluble  in  water. 
The    ethereal   salts    may  be   made    by    any   of   the   general 
methods  already  described. 

NOTE  FOR  STUDENT.  —  What  are  the  general  methods  for  the  prepa- 
ration of  ethereal  salts? 

Experiment  73.  Dissolve  40^  benzoic  acid  in  150CC  absolute  alco- 
hol. Pass  dry  hydrochloric  acid  gas  into  the  solution,  keeping  the 
latter  cool  by  surrounding  it  with  water.  When  the  solution  is 
saturated  with  hydrochloric  acid,  connect  the  flask  with  an  inverted 
condenser,  and  warm  gently  on  a  water-bath  for  half  an  hour.  Now 
add  three  or  four  volumes  of  water,  when  ethyl  benzoate  will  separate 
as  an  oil.  Wash  with  water  and  a  little  sodium  carbonate ;  and,  finally, 
dry. 

Benzoyl  chloride,  C6H5.COC1,  and  bromide,  C6H5.COBr, 
are  made  from  benzoic  acid  in  the  same  wa}^  that  acetyl  chlo- 
ride is  made  from  acetic  acid.  They  are  more  stable  than  the 
corresponding  compounds  of  the  fatty  acids-,  but  in  general 
undergo  the  same  kinds  of  change. 

Benzoyl  cyanide,  C6H5.CO.CN,  is  made  by  distilling  mer- 
curic cyanide  and  benzoyl  chloride  :  — 

2  C6H5.COC1  +  Hg(CN)2  =  2  C6H5.COCN  +  HgCl2. 

The  cyanogen  can  be  converted  into  carboxyl,  and  thus  an 
acid  of  the  formula  C6H5.CO.CO2H  obtained.  This  is  known 
as  benzoyl-formic  acid.  It  is  of  interest,  for  the  reason  that 
one  of  its  derivatives  is  also  a  derivative  of  indigo  (see 
Isatine) . 

Substitution-Products  of  Benzoic  Acid. 

Benzoic  acid  readily  yields  substitution-products  when  treated 
with  the  halogens,  nitric  acid,  and  sulphuric  acid.  The  products 
obtained  by  direct  substitution  mostly  belong  to  the  meta  series. 
Thus,  when  chlorine  acts  upon  benzoic  acid,  the  main  product 
is  meta-chlor-benzoic  acid;  nitric  acid  gives  mainly  meta-nitro- 


288  DERIVATIVES    OF   THE   BENZENE   SERIES. 

benzoic  acid;  and  sulphuric  acid  gives  mainly  meta-sulpho-ben- 
zoic  acid. 

NOTE  FOR  STUDENT.  —  Compare  this  with  the  result  of  the  direct 
action  of  the  same  reagents  on  toluene.  What  are  the  first  products 
of  the  action  of  nitric  aud  sulphuric  acids  on  toluene? 

Substituted  benzoic  acids  may  be  made,  also,  by  oxidizing 
the  corresponding  substituted  toluenes.  Thus,  chlor-toluene 
gives  chlor-benzoic  acid  ;  mtro-toluene  gives  nitro-benzoic-acid, 
etc.  :  — 

C6H4C1  .  CH3          gives     06H,C1  .  CO2H  ; 

C6H4(N02)CH3        «        C6H4(N02)C02H. 

The  three  nitro-benzoic  acids  and  the  corresponding  amido- 
benzoic  acids  may  serve  as  examples  of  the  mono-substitution 
products. 

(CO  TI 
=  C6H4  <  irX 
JNU2(o) 

Ortho-nitro-benzoic  acid  is  formed,  together  with  a  large  quan- 
tity of  the  meta  acid  and  some  of  the  para  acid,  by  treating 
benzoic  acid  with  nitric  acid,  by  oxidizing  ortho-nitro-toluene 
with  potassium  permanganate,  and  by  oxidizing  ortho-nitro- 
cinnamic  acid.  It  crystallizes  in  needles,  melts  at  147°,  and 
has  an  intensely  sweet  taste. 

CO  IT 

Meta-nitro-benzoic  acid,  C6H4  <  NO2  ^  ,  is  the  chief  prod- 

net  of  the  action  of  nitric  acid  on  benzoic  acid.  It  crystallizes 
in  laminae,  or  plates,  and  melts  at  140°  to  141°. 

CO  H 

Para-nitro-benzoic  acid,  C6H±  <  ..         ,   is  prepared  best 


by  oxidizing  para-nitro-toluene.  It  crystallizes  in  laminae, 
melts  at  238°,  and  is  much  less  easily  soluble  in  water  than 
the  ortho  and  meta  acids. 

The  determination  of  the  series  to  which  these  three  acids 


ISATINE.  289 

Delong  is  effected  by  transforming  them  into  the  amido-acids  ; 
an^  these,  through  the  cliazo  compounds,  into  the  corresponding 

hydroxy-acMs  of  the  formula  C6H4  < 

NOTE  FOR  STUDENT.  —  Give  the  equations  representing  the  action 
involved  in  passing  from  toluene  to  ortho-hydroxy-benzoic  acid  (sali- 
cylic acid)  by  the  method  above  referred  to. 

In  a  similar  way,  lines  of  connection  can  be  established 
between  the  three  hydroxy-acids  and  the  chlor-,  brom-,.  and 
iodo-benzoic  acids. 

NOTE  FOH  STUDENT.  —  What  are  the  reactions? 

The  three  hydroxy-acids,  on  the  other  hand,  have  been  made 
by  methods  which  connect  them  directly  with  the  three  bibasic 

C*O  FT 

acids  of  benzene,  C6H4  <  CO2H,  which,  in  turn,  have  been  made 
from  the  three  xylenes. 

Ortho-amido-benzoic  acid,  -»  /  CO2H 

Anthranilic  acid,  /  C*N°2  (~  C^  <  NH2(o) 

This  acid  is  made  by  reducing  ortho-nitro-benzoic  acid  with 
tin  and  hydrochloric  acid,  and  by  boiling  indigo  with  caustic 
potash.  It  has  already  been  stated  that  indigo  yields  aniline. 
Now,  as  ortho-amido-benzoic  acid  is  also  obtained,  and  this 
breaks  up  easily  into  aniline  and  carbon  dioxide, 


=  C6H5.NH2  +  C02, 
it  seems  probable  that  the  aniline  is  a  secondary  product. 

Isatine,  C8H3NO/  =  CeH^     °      C.OH-  —  Isatine  is  ob- 


tained   by  the   oxidation   of    indigo,    and   from   ortho-amido- 
benzoic  acid  as  follows  :  — 

The  amido-acid  is  converted  into  the  chloride,  the  chloride 
into   the  cyanide,  and   this   into   the   corresponding   carboxyl 


290  DERIVATIVES    OF   THE  BENZENE   SERIES. 

derivative,  which  is  the  ortho-amido  derivative  of  benzoyl- 
formic  acid.  The  ortho-amido  -benzoyl-formic  acid  thus  ob- 
tained loses  water,  and  is  converted  into  isatine.  The  changes 
are  represented  by  these  equations  :  — 


Ortho-amido-benzoic  acid.  Ortho-amidp-benzoyl 

chloride. 


(1) 

rtho-amido-benzoic  acid. 

^  w<SS>  +  AgCN  =  CA<     +  AgC1 

(3) 


Ortho-amidp-benzoyl 
cyanide. 


Ortho-amido-benzoyl- 
formic  acid. 


(4)  C6H4<-  =  CcH4<        ^  c  .OH 

Isatine. 

The  formula  given  for  isatine  represents  it  as  an  anhy- 
dride of  ortho-amido-benzoyl-formic  acid,  the  water  which  is 
given  off  being  supposed  to  be  formed  by  a  union  of  the 
two  hydrogens  of  the  amido  group  and  an  oxygen  of  car- 
bonyl.  The  formation  of  anhydrides  of  aromatic  acids  is 
a  characteristic  of  ortho  compounds.  Neither  the  meta  nor 
para  compounds  give  up  water.  We  shall  find  that  this  fact  is 
illustrated  in  the  case  of  the  bibasic  acids,  the  only  one  which 

r^r\/~\~Lj 

yields  an  anhydride  being  ortho-phthalic  acid,  C6H4<COOH/0^ 
which  gives  phthalic  anhydride,  C6H4<CQ>O.  This  ready 
formation  of  anhydrides  from  ortho  compounds,  taken  together 
with  the  fact  that  the  meta  and  para  compounds  do  not  yield 
anhydrides,  has  been  regarded  as  an  argument  in  favor  of  the 
view  that  in  the  ortho  compounds  the  two  substituting  groups 
are  actually  nearer  together  than  in  the  meta  and  para  com- 
pounds. 

The  relation  of  isatine  to  indigo  will  be  considered  briefly 
under  the  head  of  Indigo. 


HIPPURIC   ACID.  291 

Meta-  and  Para-amido-benzoic  acids  are  made  from  the 
corresponding  nitro  acids  by  reduction. 

Hippuric  acid,  benzoyl-amido-acetic  acid, 

C»HflNOs(=  CCH5.CONH.CH2C02H). 

Hippuric  acid,  as  has  already  been  seen  (Exp.  69),  occurs  in 
the  urine  of  herbivorous  animals,  as  the  cow,  horse,  camel,  and 
sheep.  Some  hippuric  acid  is  found  in  human  urine  under 
ordinary  circumstances.  If  benzoic  acid  be  taken  with  the 
food,  it  appears  as  hippuric  acid  in  the  urine,  while  derivatives 
of  benzoic  acid  appear  as  derivatives  of  hippuric  acid. 

Hippuric  acid  can  be  made  synthetically  from  benzoic  acid 
and  acetic  acid : 

1.  By  heating  glycine  with  benzoic  acid  to  160° :  — 


C6H5.COOH| 

I        I  2 

Hippuric  acid. 

2.  By  heating  benzamide  with  chlor-acetic  acid  :  — 
C6H5.CO.NHH  +  TTJ;!>CH2  =  ^  *C°;™  >  CH2  +  HC1. 

xlU2U  xiw2O 

Hippuric  acid. 

3.  By  heating  glycine  with  benzoyl  chloride  :  — 


C1.0C.C6H5  =  CH2<-65  +  HCL 


Hippuric  acid  crystallizes  from  water  in  long,  rhombic  prisms. 

It  is  decomposed  into  benzoic  acid  and  glycine  by  boiling 
with  alkalies,  and  more  readily  by  boiling  with  strong  acids 
(Exp.  69)  :  - 

=  CH2<C02H  +  C'H*-C°3H- 

NOTE  FOR  STUDENT.  —  What  relation  does  hippuric  acid  bear  to 
benzamide?  What  is  the  effect  of  boiling  acid  amides  with  alkalies? 
Write  the  equation  for  the  decomposition  of  benzamide,  and  compare 
it  with  that  for  the  decomposition  of  hippuric  acid. 


292  DERIVATIVES    OF   THE  BENZENE   SERIES. 

Toluic  acids,  C8H8O2.  —  There  are  four  acids  of  this  formula 
known  ;  viz.  :  the  three  carboxyl  derivatives  of  toluene  in  which 
the  carboxyl  takes  the  place  of  benzene  hydrogen  atoms, 

PTT 

C6H4  <       3   ,  and  an  acid  obtained  from  toluene  by  replacing  a 

V^v/o-tl- 

hydrogen   of  the  methyl  by  carboxyl,  thus,  C6H5.CH2.CO2H. 

PTF 

Ortho-,  meta-,   and  para-toluic  acids,    C6H4  <  rJ\^  are  made 

v^w  2  -ti 

by  oxidizing  the  corresponding  xylenes  with  nitric  acid  :  — 

3  0  =  CeHi  <  C02H  +  HA 
CH3 

They,  as  well  as  their  derivatives,  of  which  many  are  known, 
have  been  studied  carefully.  The  substituted  toluic  acids  may 
be  made  either  by  treating  the  acids  with  strong  reagents  or 
by  oxidizing  substituted  xylenes  :  — 

C6H3(N02)  <  ™3  +  3  O  =  C6H3(N02)  <        H  +  H2O. 

CH3 

Nitro-xylene.  Nitro-toluic  acid. 

o-Toluio   acid,  _  Just 


Phenyl-acetic  acid, 
as  benzoic  acid  may  be  regarded  as  phenyl-formic  acid,  so 
a-  toluic  acid  may  be  regarded  as  phenyl-acetic  acid.  It  is 
obtained  from  mandelic  acid,  which  is  formed  when  amygdalin 
is  treated  with  hydrochloric  acid.  It  is  prepared  from  toluene 
by  converting  this  into  benzyl  chloride,  from  which  the  cyanide 
is  made  by  boiling  with  potassium  cyanide.  The  cyanide  is 
then  treated  with  an  alkali,  and  yields  the  acid  :  — 

C6H5.CH3        +  C12       =  C6H5.CH2C1          +  HC1  ; 

Boiling  toluene.  Benzyl  chloride. 

C6H5.CH2C1    +  KCN    =  C6H5.CH2CN         +KC1; 

Benzyl  cyanide. 

C6H5.CH2CN  +  2H2O  =  C6H5  .  CH2  .  CO2H  +  NH3. 

a-Toluic  acid. 

The  acid  crystallizes  in  thin  laminae  ;  melts  at  76.5°. 


HYDKO-CiNNAMIC    ACID.  293 

NOTE  FOR  STUDENT.  —  What  would  you  expect  a-toluic  acid  to  yield 
when  oxidized?  (See  p.  246,)  What  would  you  expect  it  to  yield 
when  distilled  with  lime?  What  would  you  expect  the  three  toluic 

acids,  C6H4  <  ™-5TT,  to  yield  by  oxidation,  and  when  distilled  with  lime? 
CO2H 

(See  p.  243.) 


Oxindol,  C8H7NC)  =  C6H4  <     j    >  Co     —  Oxindol  is  ob- 

tained by  reduction  of  isatine  (see  p.  289)  ;  and  also  from 
ortho-amido-a-toluic  acid  by  loss  of  water,  in  the  same  way 
that  isatine  is  formed  from  ortho-amido-benzoyl-formic  acid. 
"When  a-toluic  acid  is  treated  with  nitric  acid,  the  para-  and 
ortho-nitro  acids  are  formed.  The  latter  is  reduced  by 
means  of  tin  and  hydrochloric  acid,  when  oxindol  is  at  once 
obtained  :  — 


Ortho-amido-a-toluic  acid.  Oxindol. 


Mesitylenic   acid,   C9H10O2{  =  t36H3  j  QQ  4j  ).  —  This   acid 

\  ^  2          / 

has  already  been  referred  to  as  the  first  product  of  oxidation 
of  mesitylene.  It  is  the  only  monobasic  acid  which  has  been 
obtained  from  mesitylene ;  and,  according  to  the  accepted 
hypothesis,  it  is  the  only  one  possible.  By  distillation  with 
lime,  it  yields  meta-xylene. 

NOTE  FOR  STUDENT.  —  Of  what  special  significance  is  the  formation 
of  meta-xylene  from  mesitylenic  acid? 

Hydro-cinnamic  acid, 

Phenyl-propionic  acid, 
Hydro-cinuaniic  or  phenyl-propionic  acid  is  obtained  by  treat- 
ing cinnaim'c  acid  with  nascent  hydrogen  :  — 

C6H5.CH.CH.C02H  +  H2  =  C6H5 .  CH2 .  CH2 .  CO,H. 

Cinnamic  acid,  Hydro-cinaaruic  acid, 

Phenyl-acrylic  acid.  Phenyl-propionic  acid. 


294  DERIVATIVES    OF   THE   BENZENE   SERIES. 

It  is  also  made  by  starting  from  ethyl-benzene,  C6H5.C2H5,  and 
using  the  same  reactions  that  are  necessary  to  transform  toluene 
into  a-toluic  acid  (see  p.  292).  It  is  a  product  of  the  decay 
of  several  animal  substances,  such  as  albumin,  fibrin,  brain,  etc. 
It  crystallizes  from  water,  in  long  needles,  which  melt  at  47°. 
It  yields  benzoic  acid  when  oxidized. 


Ortho-amido-hydro-  1  p  „      CH2  .CH2  .CO2H      T|.       .  , 

cinnamic  acid,       I  °6±±4  <  NH2(o) 

is  prepared  from  hydro-cinnamic  acid  in  the  same  way  that 
ortho-amido-a-toluic  acid  is  made  from  a-toluic  acid.  It  is 
not  obtained  in  the  free  state  ;  but,  like  the  ortho-amido 
derivatives  of  benzoyl-formic  and  of  a-toluic  acids,  it  loses 
water,  and  forms  the  anhydride, 


Hydro-carbostyril,   C6H4  <          4  >  CO.  —  Hydro-carbo- 


styril  is  made  by  treating  ortho-nitro-hydro-cinnamic  acid  with  tin 
and  hydrochloric  acid.  It  is  a  solid  which  crystallizes  in  prisms, 
melting  at  160°.  It  is  interesting  chiefly  for  the  reason  that  it 
is  closely  related  to  the  important  compound  quinoline  (which 
see).  When  treated  with  phosphorus  pentachloride,  hydro- 
carbostyril  is  converted  into  di-chlor-quinoline.  The  signifi- 
cance of  this  reaction  will  be  spoken  of  hereafter. 

BIBASIC  ACIDS,  CnH2n_10O4. 

The  simplest  acids  of  this  group  are  the  three  phthalic  acids, 
which  are  the  di-carboxyl  derivatives  of  benzene,  belonging  to 
the  ortho,  meta,  and  para  series. 


Phthalic  acid, 

Ortho-phthalic  acid,  /  "  "^V"  ^CO2H 
acid  was  the  first  of  the  three  acids  of  this  composition  dis- 
covered;  and,  as  it  was  obtained  from  naphthalene,  it  was 
named  phthalic  acid.  In  addition  to  its  formation  from 


PHTHAL1C    ANHYDKIDE.  295 

naphthalene   may  be  mentioned  that   from    alizarin    and    pur- 

OTT 

purin  ;    and   from  ortho-toluic  acid,  C6H4<  nr/HCo)'  ^J  oxida- 
tion with  potassium  permanganate. 

Experiment  74.  Mix  40s  naphthalene  and  80s  potassium  chlorate, 
aucl  add  this  mixture  gradually  to  400s  ordinary  concentrated  hydro- 
chloric acid.  Naphthalene  tetra-chloride,  C10H8.C14,  is  formed  in  this 
reaction.  Wash  with  water.  Gradually  add  400s  ordinary  concen- 
trated nitric  acid  (sp.  gr.  1.45),  and  boil  in  a  flask  connected  with  an 
inverted  condenser.  When  all  is  dissolved,  evaporate  the  nitric  acid; 
and,  finally,  distil  the  residue.  Phthalic  anhydride  passes  over.  Ee- 
crystallize  from  water.  This  will  be  used  for  other  experiments. 

Phthalic  acid  forms  rhombic  crystals,  which  melt  at  213°  or 
lower,  according  to  circumstances,  as,  when  heated,  it  breaks 
up  gradually,  even  below  the  melting-point,  into  water  and  the 
anhydride  which  melts  at  128°.  Distilled  with  lime,  it  yields 
benzene  ;  though,  by  selecting  the  right  proportions,  benzoic 
acid  may  be  obtained  :  — 


(1)  C6H4 

(2)  C6H4  <  =  c6H5  .  C02H  +  C02. 

Phthalic  acid  is  decomposed  b}^  chromic  acid,  yielding  only 
carbon  dioxide  and  water.  Hence,  ortho-xylene,  when  treated 
with  chromic  acid,  does  not  yield  phthalic  acid.  By  boiling 
ortho-xylene  with  nitric  acid,  however,  it  yields  ortho-toluic 

r^TT 
acid,    C6H4<C03II(0),   and    this   may    be    oxidized   to    phthalic 

acid  ~by  treatment  with  potassium  permanganate. 

r*f\ 

Phthalic  anhydride,  CtiH4  <  ~,Q  >  O,  is  formed  by  heat- 

ing phthalic  acid.  It  forms  long  needles,  which  melt  at  128°. 
Treated  with  phenols,  it  forms  the  compounds  known  as  phtha- 
le'ins  (which  see)  . 


296  DERIVATIVES    OF   THE   BENZENE   SERIES. 

formed  b  oxi- 


,-1         COH,  . 

Meta-phthalic  acid,  )  CO,H(m)' 

dizing  either  meta-xylene  or  meta-toluic  acid  with  chromic 
acid  ;  by  distilling  meta-benzene-disulphonic  acid  with  potas- 
sium cyanide,  and  boiling  the  resulting  dicyanide  with  an 
alkali. 

NOTE  FOR  STUDENT.  —  Write  the  equations  representing  the  action 
involved  in  passing'  from  meta-benzeue-disulphonic  acid  to  isophthalic 
acid.  Into  which  dihydroxy-beuzene  is  this  same  disulphonic  acid 
converted  by  meltiiig  it  with  caustic  potash? 

The  acid  is  formed,  further,  by  treating  meta-sulpho-benzoic 
acid  with  sodium  formate  :  — 


Potassium  sulpho-  Potassium  iso- 

benzoate.  phthalate. 

This  reaction  is  of  importance,  for  the  reason  that  the  same 
sulpho-benzoic  acid,  which  is  thus  converted  into  isophthalic 
acid,  can  also  be  converted  into  one  of  the  three  hydroxy- 
benzoic  acids  ;  and  thus  connection  is  established  between 
the  latter  and  isophthalic  acid  and  meta-xylene. 

Isophthalic  acid  crystallizes  in  fine  needles  from  water.  It 
melts  above  300°,  and  is  not  converted  into  an  anhydride. 


Terephthalic  acid,    t  ~  TT       CO2H  ^        ,,,    ,.        .  , 

_  '    V  C6Ht  <  fvv  %T/  ^  •  —Terephthalic  acid 

Para-phthalic  acid,  I  CO2Ho) 

is  formed  by  oxidation  of  the  oil  of  turpentine,1  cyrnene,  para- 
xvlene,  and  para-toluic  acid  ;  by  heating  a  mixture  of  potassium 
para-sulpho-benzoate  and  sodium  formate  :  — 


Potassium  para-  Potassium  tere- 

sulpho-benzoate.  phthalate. 

1  The  prefix  tere  is  derived  from  the  Latin  terebinthinus,  turpentine. 


PHENOL-ACIDS    OF   THE   BENZENE   SERIES.  297 

Para-sulpho-benzoic  acid  is  converted  into  one  of  the  three 
hydroxy-benzoic  acids  by  caustic  potash.  In  the  para  as  well 
as  the  meta  series,  the  lines  of  connection  indicated  below  have 
been  established :  — 


}•*-*•  3 

I  1         I 

I       ro-pr       I      rw 

/"(  TT      ^    Vy  V72111     .^ O  TJ    ^  ^^^S 

JH4<C02H^  <C02H 


„  T      OH    rw    .SO8H 

CoH4<OH«s        C^<s03H 

Terephthalic  acid  is  a  solid  which  is  practically  insoluble  in 
water.  It  sublimes  without  melting  and,  like  isophthalic  acid, 
yields  no  anhydride. 

HEXABASIC  ACID. 

Mellitic  acid,  CuH«Oa[=  C«(OO,H)«]. — This  acid  occurs 
in  nature  in  the  form  of  the  aluminium  salt,  as  the  mineral 
honey-stone  or  mellite.  The  mineral  is  rare,  and  is  found  in 
beds  of  lignite.  Mellitic  acid  has  been  made  by  direct  oxida- 
tion of  carbon  with  potassium  permanganate,  and  by  oxidation 
of  hexa-methyl-benzene,  C6(CH3)6.  By  ignition  with  soda-lime 
it  is  converted  into  benzene  and  carbon  dioxide  :  — 

CC(C02H)6  =  C6H6  +  6  CO2. 

PHENOL-ACIDS,  OR  HYDROXY- ACIDS  OF  THE  BENZENE  SERIES. 

It  will  be  remembered  that  the  alcohol  acids  or  hydroxy- 
acids  of  the  paraffin  series  form  an  important  class,  including 
such  compounds  as  glycolic,  lactic,  malic,  tartaric,  and  citric 
acids.  The  peculiarity  of  these  compounds  is  their  double 
character.  They  are  at  the  same  time  alcohols  and  acids, 
though  the  acid  properties  are  more  prominent  than  the  alco- 


298  DERIVATIVES    OF   THE   BENZENE   SERIES. 

holic.  The  hydroxy-acids  of  the  benzene  series  bear  the  same 
relations  to  the  benzene  hydrocarbons  that  the  hydroxy-acids 
already  considered  bear  to  the  paraffins.  The  simplest  are 
those  which  contain  one  hydroxyl  and  one  carboxyl  in  benzene, 

OTT 

having  the  formula  C6H4  <  . 

CytJg-tL 

MONOHYDROXY-BENZOIC    ACIDS,    C7H6O3. 

Salicylic  acid,  )  OH  _  s  V     1* 

Ortho-hydroxy-benzoic  acid,  >  CO2H(o)' 

acid  is  found  in  the  form  of  an  ethereal  salt  of  methyl,  in  the 
oil  of  wintergreen,  prepared  from  the  blossoms  of  Gaultheria 
procumbens.  It  is  formed  in  a  number  of  ways,  among  which 
the  following  should  be  specially  mentioned  :  — 

1.  By  converting   ortho-amido-benzoic  acid  into   the   diazo 
compound,  and  boiling  with  water. 

NOTE    FOB    STUDENT.  —  Give   the  equations  representing  the  re- 
actions. 

2.  By  melting  ortho-sulpho-benzoic  acid  with  caustic  potash. 
NOTE  FOR  STUDENT.  —  Write  the  equation. 

3.  By  passing  carbon  dioxide  over  sodium  phenolate  heated 
to  180°  :  - 

2  C6H5  .ONa  +  C02  =  C6H4  <  °^T    +  C6H5OH. 

CO^IXa 

4.  By  heating  phenol  with  tetra-chlor-methane  and  alcoholic 
potash  :  — 


C6H5  .OH  +  CC14  +  6  KOH  =  C6H4  <  ™     +  4  KC1  +  4  H2O. 

CO2-K- 

5.  By  saponifying  the  methyl  salicylate  found  in  the  oil  of 
wintergreen  :  — 


SALICYLIC   ACID. 


299 


Experiment  75.  Boil  30CC  to  40CC  oil  of  wintergreen  with  moder- 
ately strong  caustic  potash  in  a  flask  connected  with  an  inverted  con- 
denser. When  it  is  dissolved,  acidify  with  hydrochloric  acid.  Filter 
off  the  salicylic  acid  which  separates,  and  recrystallize  from  water. 

Experiment  76.  Dissolve  50*?  to  60s  phenol  in  the  equivalent  quan- 
tity of  caustic  soda;  Evaporate  to  dryness.  Powder,  and  put  the  salt 
in  two  or  three  small,  flat-bottom  flasks.  Connect  these  with  each 
other,  and  pass  dry  carbon  dioxide  through  them.  For  the  purpose  of 
heating  them,  it  is  best  to  place  them  in  an  air-bath.  Heat  at  first  to 


Fig.  17. 

100°,  and  then  gradually  let  the  temperature  rise  to  180°.  Finally,  heat 
to  220°  to  250°.  After  cooling,  dissolve  the  mass  in  not  too  much 
water,  and  add  hydrochloric  acid.  Salicylic  acid  will  separate.  Re- 
crystallize  from  water,  with  the  addition  of  bone-black. 

Experiment  77.  Make  a  solution  of  40&  phenol  and  80s  sodium 
hydroxide  in  120CC  to  140CC  water.  Add  gradually  602  chloroform, 
constantly  shaking  the  mixture.  The  solution  changes  color,  and 
becomes,  finally,  deep  red.  The  flask  should  be  arranged  as  shown 
in  Fig.  17,  to  prevent  loss  of  chloroform  in  consequence  of  the  spon- 


300  DERIVATIVES    OF   THE   BENZENE   SERIES. 

taneous  elevation  of  temperature.  After  all  the  chloroform  is  used 
up,  and  the  action  is  over,  boil  for  half  au  hour.  Add  dilute  hydro- 
chloric or  sulphuric  acid  until  the  solution  has  an  acid  reaction.  A 
thick,  red-colored  oil  will  be  thrown  down.  Boil  by  passing  steam 
through  the  liquid,  as  in  Exp.  67.  A  light-colored  oil  will  pass  over. 
This  is  the  aldehyde  of  salicylic  acid,  together  with  some  unacted-upon 
phenol.  Dissolve  in  ether,  and  shake  this  with  an  aqueous  solution 
of  mono-sodium  sulphite,  when  the  aldehyde  unites  with  the  sulphite. 
Separate  the  ether  solution  of  phenol  from  the  lower  water  solution, 
and  acidify  the  latter  with  hydrochloric  or  sulphuric  acid,  when  sali- 
cylic aldehyde  is  thrown  down  as  an  oil.  Put  the  oil  in  a  silver  (or 
iron)  basin  with  208  to  30s  caustic  potash  and  a  little  water,  and  keep 
the  mass  in  fusion  for  an  hour  or  two.  By  this  means  the  aldehyde  is 
oxidized  to  the  acid.  Finally,  dissolve  the  mass  in  water,  acidify,  and 
filter  off  the  salicylic  acid  which  separates. 

The  action  of  chloroform  on  phenol  in  the  presence  of  caustic 
soda  is  analogous  to  that  of  tetra-chlor-me thane.  It  is  repre- 
sented in  this  way  :  — 

CGH5.ONa      -f  3  NaOH  +  CHC13 

+2H20. 

This  reaction  is  of  general  application  to  phenols,  and  affords 
a  very  convenient  method  for  the  preparation  of  the  phenol- 
acids. 

Salicylic  acid  crystallizes  from  hot  water  in  fine  needles.  It 
melts  at  155°  to  156°. 

When  heated,  it  breaks  up  into  phenol  and  carbon  dioxide  :  — 

=  CeH5.OH  +  C02. 

-2 

With  ferric  chloride,  its  aqueous  solution  gives  a  character- 
istic dark  violet-bine  color.  Free  salicylic  acid  is  antiseptic, 
preventing  decay  and  fermentation.  It  is  therefore  used  for 
preserving  organic  substances. 

Salicylic  acid  forms  salts  of  the  general  formula  C(iH4<  ; 

C  O.i  iVL 

and,  with  the  alkalies,  compounds,  in  which  both  the  phenol  by- 


SALICYLIC   ACID.  801 

drogen   and   the   acid  hydrogen   are   replaced   by   metals,    as 

C6H4<OK^.      Salts   of    the   latter  order,  which   contain   the 
COglv 

metals  of  the  alkaline  earths,  are  decomposed  by  carbon 
dioxide.  Salicylic  acid  forms  ethereal  salts  of  the  general 

formula  C6H4<^R,  of  which  methyl  salicylate,  ceH4<co.CH.' 
is  the  best-known  example.  It  forms,  also,  ether-acids  of  the 
general  formula  C6H4  <  ??  ;  and,  finally,  compounds  of  the 

general  formula  C6H4  <  ^  '    . 

C--  Wo  Ab 

A  very  large  number  of  substitution-products  and  other 
derivatives  of  salicylic  acid  have  been  studied  ;  but  they  need 
not  be  considered  here. 

That  salicylic  acid  belongs  to  the  ortho  series,  follows  from 
the  following  facts  :  — 

Ortho-tolueue-sulphonic  acid  has  been  converted  into  ortho- 
sulpho-benzoic  acid,  and  this  into  salicylic  acid.  Further,  the 
same  toluene-sulphonic  acid  has  been  converted  into  ortho-toluic 
acid,  which,  by  oxidation,  yields  phthalic  acid. 


Ortho-toluene-sulphonic  Ortho-sulpho-benzoic 

acid.  acid. 


Potassium  salicylate. 


(4) 


4  =  I 

Ortho-toluic  acid. 


PhthaHc  acid. 


302  DERIVATIVES    OF   THE   BENZENE   SERIES. 


Salicylid,  C7H4O2(  =  C6H4  <   I     (?)   ,  is  a  substance  obtained 

V  CO      J 

from  salicylic  acid  by  the  abstraction  of  water.  This  ability  to 
form  anhydrides  is  in  some  way  connected  with  the  ortho  rela- 
tion, as  the  two  isomeric  hydroxy-acids  do  not  yield  anhydrides. 

NOTE  FOR  STUDENT.  —  Compare  the  three  phthalic  acids  in  this 
respect. 

Oxybenzoic    acid,  ^  .OH 

•«/r  j_     i      -,  i  -  -if  WtLt  <  ^/^  TT      • 

Meta-nydroxy-benzoic    acid,  J  CO2H(m) 

acid  is  made  from  meta-amido-benzoic  and  meta-sulpho-benzoic 
acid  by  the  usual  reactions. 

It  crystallizes  from  water  in  needles  united  to  form  wart-like 
looking  masses.  It  gives  no  color  with  ferric  chloride.  Its 
connection  with  meta-phthalic  (isophthalic)  acid  and  meta-xylene 
is  effected  by  means  of  the  transformations  tabulated  on  p.  297  ; 
that  is  to  say,  the  same  sulpho-benzoic  acid  which,  by  melting 
with  caustic  potash,  yields  oxybenzoic  acid,  by  melting  with 
sodium  formate,  yields  isophthalic  acid.  Therefore  oxybenzoic 
acid  is  a  meta  compound. 


Para-oxybenzoic  acid,  •>  OH 

_         ,      T  ,  .          •  -,    c  ^e-H-i  <  ~,^  T-T      •  —  Fara- 

Para-hydroxy-benzoic  acid,  J  CO2H(p) 

oxybenzoic  acid  is  formed  from  the  corresponding  amido  and 
sulpho-benzoic  acids  ;  by  treating  various  resins  with  caustic 
potash  ;  from  anisic  acid  (which  see)  ,  by  heating  with  hydriodic 
acid  ;  by  heating  potassium  phenolate  in  a  current  of  carbon 
dioxide. 

NOTE  FOR  STUDENT  —  Notice  the  fact  that,  while  sodium  phenolate, 
when  heated  in  a  current  of  carbon  dioxide,  yields  salicylic  acid, 
potassium  phenolate,  under  the  same  circumstances,  yields  para-oxy- 
benzoic  acid. 

Its  aldehyde  is  formed,  together  with  salicylic  aldehyde,  by 
treating  phenol  with  chloroform  and  caustic  soda  (see  Exp.  77). 


PROTOCATECHUiC    ACID.  303 

The  reasons  for  considering  para-oxybenzoic  acid  as  a  mem- 
ber of  the  para  series  are  similar  to  those  which  show  that 
oxy  benzole  acid  is  a  meta  compound.  The  same  sulpho-benzoic 
acid  which  yields  para-oxybenzoic  acid,  also  yields  terephthalic 
acid. 

Anisic  acid,  |  C  H  <  OCH3     .  —  Anisic 

Para-methoxy-benzoic1  acid,  /  CO2H(p)' 

/-Vrf^tTT 

acid  is  formed  by  the  oxidation  of  anethol,   C6H4  <  ^      3,   a 

^3H5 

phenol  ether  contained  in  anise  oil.  It  is  made  by  heating 
para-oxybenzoic  acid  with  caustic  potash  and  methyl  iodide. 
As  the  formula  indicates,  it  is  the  methyl  ether  of  para-oxy- 
benzoic acid. 

Dl-HYDROXY-BENZOIC    ACIDS,    C7H6O4. 

Protocatechuic  acid,  CGH:i  {  LQ  ^,  is  a  frequent  product 
of  the  fusion  of  organic  substances  with  caustic  potash.  Thus, 
the  following  substances,  among  others,  yield  it:  oil  of  cloves, 
piperic  acid,  catechin,  gum  benzoin,  asafoetida,  vanillin,  etc. 
It  is  made  from  sulpho-oxybenzoic  acid,  and  from  sulpho-para- 
oxy benzole  acids  by  fusing  with  caustic  potash. 

NOTE  FOR  STUDENT.  —  What  analogy  is  there  between  the  fact  that 
protocatechnic  acid  is  formed  from  sulpho-oxybenzoic  acid  and  from 
sulpho-para-oxybenzoic  acid,  and  the  fact  that  pseudocumene  is  formed 
from  brom-meta-xylene  and  from  brom-para-xylene?  What  conclusion 
may  be  drawn  regarding  the  relations  of  the  two  hydroxyl  groups,  and 
the  carboxyl  in  protocatechnic  acid? 

By  distillation  with  lime,  protocatechuic  acid  breaks  up  into 
pyrocatechin  and  carbon  dioxide  :  — 

(OH 

C6H3jOH      -Qftj       [  +  C02. 
(  rn  TJ  I  vti 

Pyrocatechin. 

1  Methoxy  is  derived  from  methoxyl,  the  name  given  to  the  ether  group,  OCH3.  In 
a  similar  way  OC2H5  is  called  ethoxyl ;  OC0H0,  phenoxyl,  etc. 


304  DERIVATIVES    OF   THE   BENZENE   SERIES. 

rOCH3 

Vanillic  acid,  C6H5  \  OH     ?    is   formed   by   oxidation   of 

(  C02H 
vanillin,  which  is  the  corresponding  aldehyde.     It  is  the  mono- 

methyl  ether  of  protocatechuic  acid. 

/  f  OCH3\ 

Vanillin,  C8H8O3(  =  C6H:J  OH      ),  occurs  in  nature,  as  a 

V  I  CHO  J 

crystalline   coating,    on   the  fruit  of  the  vanilla.      It  is  made 

artificially  by  treating  the  ether,  C6H4<  °^3},  with  chloroform 
and  caustic  soda. 

Tm-HYDROXY-BENZOIC    ACIDS,    C7H6O5. 

Gallic  acid,  C7H6O5f  =  C6H2V  —  Gallic  acid  occurs 


in  sumach,  and  in  Chinese  tea,  and  many  other  plants.  It  is 
formed  by  boiling  tannin  or  tannic  acid  with  sulphuric  acid  ;  by 
melting  brom-protocatechuic  acid  with  caustic  potash  :  — 

C6HJ  (OH)2  +  KOH  =  C6HJ  ^^  +  KBr. 
(C02H  °2H 

Brom-protocatechuic  Gallic  acid. 

acid. 

It  is  best  prepared  from  gall  nuts  by  fermentation  of  the 
tannin  contained  in  them. 

Gallic  acid  is  easily  soluble  in  water.  Its  solution  gives, 
with  a  little  ferric  chloride,  a  blue-black  precipitate,  which 
dissolves  i-n  excess  of  ferric  chloride,  forming  a  dark  green 
solution.  It  readily  reduces  metallic  salts  in  solution.  When 
heated,  it  yields  pyrogallol  (pyrogallic  acid)  and  carbon  di- 

oxide :  - 

=  C6H3(OH)3  +  C0a. 


Tannic  acid,  tannin,  CUHWO<}.  —  This  substance  occurs 
in  gall  nuts,  from  which  it  is  extracted  in  large  quantities.  It 
is  an  amorphous  powder.  It  is  markedly  astringent  in  its  action 


KETONES.  305 

on  the  mucous  membranes.  It  is  soluble  in  water,  the  solution 
giving,  with  ferric  chloride,  a  dark  blue-black  color.  Tannin  is 
used  extensively  in  medicine,  in  dyeing,  and  in  the  manufacture 
of  ink.  Its  relation  to  gallic  acid  is  indicated  by  the  following 
equation  :  -  g  ^  =  ^^  +  ^ 

Gallic  acid.  Tannin. 

KETONES  AND  ALLIED  DERIVATIVES  OF  THE  BENZENE  SERIES. 

The  ketones  of  the  benzene  series  are  strictly  analogous  to 
those  of  the  paraffin  series,  and  they  are  made  in  the  same  way. 
Acetone  is  made  by  distilling  calcium  acetate  :  — 


CH«.COO 


CHCOO 


>Ca 


V^n3 

~  CH, 


>  CO  +  CaCOo. 


Acetone. 

So,  also,  benzophenone  or  diphenyl  ketone  is  made  by  distill- 
ing calcium  benzoate :  — 


C6H5fCOO 


>Ca 


CfiH 


5  >  CO  -f-  CaCO3. 


Benzophenone. 

Further,  by  distilling  mixtures  of  the  salts  of  two  fatty  acids, 
mixed  ketones  are  obtained  :  — 

CH3  .COJOMJ         =  CH3  >  CQ       M2COs 
C2H5jCOOM!  C2H5 

Ethyl-methyl 
ketone. 

And,  similarly,  mixed  ketones  containing  one  residue  of  a 
benzene  Irydrocarbon  and  one  of  a  paraffin  ;  or,  two  different 
residues  of  benzene  Irydrocarbons  may  be  obtained  thus  :  — 

/i\  C6H5.COOM          C6H5     rY, 

CH3.COOM        -   CH^      '  + 

Phenyl-methyl  ketone, 
Acetopheuone. 

C6H5.COOM 


4       COOM  77 

Phenyl-tolyl-ketone. 

The  individual  ketones  need  not  be  considered. 


306  DERIVATIVES    OF   THE   BENZENE   SERIES. 

QuiNONES. 

The  quinones  are  peculiar  bodies  which  in  some  ways  are 
allied  to  the  ketones.  The  simplest  example  of  the  class,  and 
the  one  best  known,  is  called  quinone.  Its  formula  is  C6H4O2, 
aud  it  therefore  appears  to  be  benzene  in  which  two  hydrogen 
atoms  are  replaced  by  two  oxygen  atoms.  All  quinones  bear 
this  relation  to  the  hydrocarbons,  of  which  they  may  be  regarded 
as  derivatives. 

Quinone,  C6H4O2,  is  formed  by  the  oxidation  of  qninic  acid, 
hydroquinone,  para-diamido-benzene,  and  some  other  benzene 
derivatives  in  which  two  substituting  groups  occupy  the  para 
position  relatively  to  each  other. 

It  forms  long,  yellow  prisms ;  sublimes  in  golden-yellow 
needles. 

Hydriodic  acid  reduces  quinone  to  hydroquinone  :  — 

C6H402  +  2  HI  =  C6H,(OH)2  +21. 

The  easy  transformation  of  hydroquinone  into  quinone,  and 
the  opposite  transformation  of  quiuone  into  hydroquinone,  as 
well  as  the  formation  of  quinone  from  other  para  compounds, 
force  us  to  the  conclusion  that  the  oxygen  atoms  in  quinone 
are  in  the  para  position  relatively  to  each  other.  Quinone 
appears,  therefore,  as  a  substance  containing  two  carbonyl 
groups  which  are  united  by  means  of  hydrocarbon  residues, 
as  indicated  in  the  formula,  — 

O 

c 

pn  HCX    XCH 

C2H2<^>C2H2    or          |  ! 

co  HCV       yCH 

XCX 
O 

A  substance  of  this  kind  may  be  called  a  di-ketone,  and  may 
be  regarded  as  derived  from  a  dibasic  acid  in  the  same  way  that 


PYlilDINE  BASES.  307 


a  simple  ketone  is  derived  from  a  monobasic  acid.     Thus,  the 

POOTT 

calcium  salt  of  an  acid  of  the  formula  C2H2  <  ought,  ac- 

\^\_)\J  tl 

cording  to  this  view,  to  yield  quiuone  by  distillation  :  — 


CH<C°i°>Ca 

2    [co 


2CaCO 


Several  quinones  have  been  studied.  Under  the  head  of 
Anthracene,  we  shall  meet  with  an  important  one  called  anthra- 
quinone,  which  has  been  made  by  such  reactions  as  prove  it  to 
be  a  di-ketone  in  the  sense  in  which  this  expression  is  explained 
above. 

PYKIDINE  BASES,  CnH2n_5N. 

In  the  manufacture  of  bone-black,  bones  are  subjected  to  dry 
distillation,  when  an  oil  passes  over  which  is  known  as  bone  oil. 
This  oil  is  a  complex  mixture  of  substances,  several  of  which 
have,  however,  been  isolated.  Among  the  pure  substances 
which  have  been  obtained  from  bone  oil  may  be  mentioned 
pyridine,  picoline,  lutidine,  and  collidine.  All  these  compounds 
contain  nitrogen  ;  and,  starting  with  pyridine,  they  form  a 
homologous  series  :  — 

Pyridine       .......  C5H5N. 

Picoline  ........  C6H7N. 

Lutidine       .......  C7H9N. 

Collidine      .......  C8HUN. 

Pyridine,  C5H5N.  —  Besides  being  formed  in  the  distillation 
of  bones,  pyridine  has  recently  been  made  in  several  ways, 
some  of  which  enable  us  to  form  a  conception  in  regard  to 
its  relations  to  other  substances  which  have  been  considered. 
Great  interest  in  the  substance  and  its  derivatives  has  been 


808  DERIVATIVES    OF   THE   BENZENE    SERIES. 

aroused  by  the  observation  that  several  of  the  alkaloids  which 
occur  in  nature,  such  as  quinine,  cinchonine,  nicotine,  etc., 
when  oxidized,  yield  acids  containing  nitrogen,  which  bear  to 
pyridine  the  same  relations  that  benzoic,  phthalic  acids,  etc., 
bear  to  benzene.  Thus,  by  oxidizing  nicotine,  nicotinic  acid  is 
obtained.  This  has  the  formula  C6H5NO2 ;  and,  when  distilled 
with  lime,  it  breaks  up  into  pyridine  and  carbon  dioxide :  — 

C6H5N02  =  C5H5N  +  C02. 

Nicotinic  acid.        Pyridine. 

This  naturally  leads  to  the  conclusion  that  nicotinic  acid  is 
pyridine-carbonic  acid,  C5H4N.CO2H,  which  bears  to  pyridine 
the  same  relation  that  benzoic  acid  bears  to  benzene,  acetic 
acid  to  marsh  gas,  etc. 

Pyridine  is  formed  :  — 

1 .  By  treating  iso-amyl  nitrate  with  phosphorus  pentoxide  :  — 

C5Hn.N03  =  C5H5N  +  3H20. 

2.  By  conducting  acetylene  and  hydrocyanic  acid  together 
through  a  tube  heated  to  redness  :  — 

2  C2H2  +  HCN  =  C5H5N. 

It  is  a  liquid  with  a  peculiar,  sharp,  characteristic  odor.  It 
boils  at  116.7°. 

It  unites  with  acids  forming  salts. 

It  has  been  suggested  that  pyridine  is  related  to  benzene  ; 
and  that  it  may  be  regarded  as  the  hydrocarbon  in  which  one 
of  the  six  CH  groups  is  replaced  by  a  nitrogen  atom,  as  repre- 
sented in  the  formulas 

H  H 

/C  C 

Trp  /  \P~tT  TIP/         \PTI 

JtlV/  OXJ.  JtlV^  V^il 

I  I          and  I  | 

HCX    /CU  HCX     /CR 

H 


TERPENES.  309 

This  view  has  suggested  various  lines  of  investigation.  Thus, 
if  the  above  formula  really  represents  the  relations  between 
benzene  and  pyridine,  it  is  clear  that  the  existence  of  three 
isomeric  mono-substitution  products  of  pyridine  ought  to  be 
possible.  Thus,  there  should  be  three  methyl-pyridines  or 
picolines,  three  pyridine-carbonic  acids,  etc.  The  three  pico- 
lines should  correspond  to  the  formulas 

H  H  CH3 

/c  c  c^ 

HCX      XCH  HCT      XC.CH3        nc/    XCH 

I  i  II  !  I 

HCX     /C.CH,         HCX     /CK  HCX     /CH 

Ortho-picoline.  Meta-piooline.  Para-picoline. 

All  three  picolines  are  known;  and,  by  oxidation,  they  are 
converted  into  the  three  pyridine-carbonic  acids,  C5H4N.CO2H  ; 
and  these,  when  distilled  with  lime,  yield  pyridine  and  carbon 
dioxide. 

The  pyridine  bases  unite  with  two,  four,  or  six  atoms  of 
hydrogen.  The  addition-products  thus  formed  are  believed 
to  exist  in  the  alkaloids. 

Piperidine,  C5HnN,  a  base  found  in  piperine,  a  constituent 
of  pepper,  has  been  shown  to  be  hexa-hydro-pyridine. 

Nicotine  is  probably  of  similar  structure. 

Valuable  results  may  be  expected  from  the  further  investiga- 
tion of  pyridine  and  its  derivatives. 

TERPENES,  C10H16. 

In  nature,  particularly  in  the  coniferous  plants,  occur  several 
isomeric  hydrocarbons,  which  are  known  by  the  common  name 
terpene.  These  substances  are  very  susceptible  to  the  action 
of  reagents,  and  hence  undergo  many  changes.  One  of  the 
most  common  changes  is  polymerisation.  Thus,  when  a  terpene 
is  heated  in  a  sealed  tube,  or  is  shaken  with  concentrated  sul- 


310  DERIVATIVES    OF   THE   BENZENE    SERIES. 

phuric  acid,  or  with  boron  fluoride  and  other  substances,  it  is 
converted  into  polymeric  modifications  of  the  formulas  C15H24 
and  C20H32.  The  terpenes  unite  with  hydrochloric  and  hydro- 
bromic  acids,  forming  compounds,  C10H16.HC1  and  C10H16.2  HC1. 

Oil  of  turpentine,  terebenthene,  C10H1G.  —  This  oil  is 
obtained  by  distilling  turpentine,  a  resinous  substance  which 
exudes  from  incisions  in  the  bark  of  various  species  of  the 
pine,  larch,  fir,  etc.,  especially  from  the  pine.  The  oil  consists 
largely  of  a  hydrocarbon,  C1&H16.  The  oils  obtained  from  dif- 
ferent species  of  trees  differ  somewhat  in  their  properties. 

Among  the  more  interesting  chemical  transformations  of  oil 
of  turpentine,  the  following  may  be  mentioned  :  It  absorbs 
oxygen  from  the  air ;  dilute  nitric  acid  oxidizes  it  readily,  con- 
verting it  into  acetic,  propionie,  butyric,  oxalic,  para-toluic, 
terephthalic  acids  and  some  other  acids ;  bromine  and  iodine 
convert  it  into  cymene. 

Oil  of  turpentine  is  used  in  the  manufacture  of  varnishes  on 
account  of  its  solvent  power  for  resins.  It  is  also  used  in 
medicine. 

The  reactions  above  enumerated  indicate  clearly  that  there 
is  a  close  relation  between  cymene  and  oil  of  turpentine.  This 
is  shown  by  the  fact  that  it  is  so  readily  converted  into  cymene, 
and  that  it  yields  para-toluic  and  terephthalic  acids  by  oxida- 
tion. It  has  therefore  been  suggested  that  oil  of  turpentine  is 
a  hydrogen  addition-product  of  cymene,  of  the  formula 

CH3 
/C 

HC/     XCH2 
or  ,  , 

R2C  CH 

xcr 

C3H7 

"We  know  nothing  in  regard  to  the  causes  of  the  isomerism  of 
the  different  terpenes. 


CAMPHOR.  311 

It  should  be  observed  that  the  above  formula  furnishes  no 
explanation  of  the  fact  that  oil  of  turpentine  acts  like  an  un- 
saturated  compound. 

Terpene  hydrochloride, •»  _,  .  „„.      ,     ,      ,,    . 

V  C10H16 .  HC1. — When  hydrochloric 
Artificial  camphor, 

acid  gas  is  conducted  into  oil  of  turpentine,  a  curious  solid 
known  as  artificial  camphor  is  formed.  It  looks  like  ordinary 
camphor,  and  has  a  very  similar  oclor.  When  heated  alone,  or 
with  bases,  it  gives  off  hydrochloric  acid,  and  a  terpene  different 
from  the  oil  of  turpentine  is  formed. 


CAMPEOR. 

Borneol,  Borneo  camphor,  C10H18O.  —  Borneo  camphor 
is  a  substance  found  in  cavities  in  a  tree  (Dryobalanops  cam- 
phora)  which  grows  in  Borneo,  Sumatra,  etc.  It  may  be  made 
by  treating  ordinary  camphor  with  sodium  :  — 


2  C10H16O  +  2  Na  =  C10H17ONa  + 

Ordinary  Sodium  compound    Sodium  compound 

camphor.  of  borneol.  of  ordinary 

camphor. 

The  relation  between  the  two  kinds  cf  camphor  is  shown  better 
by  the  equation  :  — 


-f-  H2  =  C10H18O. 

Ordinary  Borneol. 

camphor. 

Camphor,  laurinol,  C10H16O  —  This  is  the  substance  ordi- 
narily called  camphor.  It  is  obtained  in  China  and  Japan  from 
different  species  of  the  genus  camphora  of  the  laurus  family,  by 
distilling  the  finely-cut  wood  with  water  vapor.  It  is  purified 
by  sublimation. 

Camphor  forms  hexagonal  crystals  ;  melts  at  1  75°,  and  boils 
at  204°.  It  is  only  slightly  soluble  in  water  ;  easily  soluble  in 
alcohol. 

Boiled  with  iodine,  hydriodic  acid  gas  is  given  off  and  cymene 


312  DERIVATIVES    OF   THE   BENZENE   SERIES. 

is  formed.      Phosphorus  pentoxide  decomposes  camphor  into 
cymene  and  water  :  — 

C10H160  =  C10H14  +  H20. 

Camphor.  Cymene. 

The  same  decomposition  is  effected  by  heating  camphor  with 
concentrated  hydrochloric  acid  to  170°.  It  will  be  seen  that, 
as  far  as  the  composition  is  concerned,  the  difference  between 
a  terpene  and  camphor  is  one  atom  of  oxygen :  — 

CioH16.  C10H16O. 

Terpene.  Camphor. 

The  relation  between  the  substances  is  undoubtedly  a  close 
one,  as  is  shown  by  the  formation  of  cymene  from  both.  It  is 
stated  that  a  substance  closely  resembling  camphor  has  been 
made  by  oxidizing  the  terpene  known  as  camphene,  which  is 
formed  by  shaking  oil  of  turpentine  with  sulphuric  acid. 


CHAPTER    XVI. 

DI-PHENYL-METHANE,  TRI-PHENYL-METHANE, 

TETRA-PHENYL-METHANE,   AND   THEIR 

DERIVATIVES. 

As  we  have  seen,  toluene  may  be  regarded  either  as  metlryl- 
benzene  or  phenyl-methane.  Of  course,  according  to  all  that 
is  known  regarding  similar  substances,  the  two  views  are  identi- 
cal. Regarding  it,  for  our  present  purpose,  as  phenyl-methane, 

f  C6H5 

H 
we  may  write  its  formula  thus  :    C  -j  TT 

lH 

This  suggests  the  possibility  of  the  existence  of  such  sub- 
stances as 


Di-phenyl-methane 


C6H5 

Tri-phenyl-methane    .......     c      C(;H5, 

C6H5 

^H 

rC6H5 

and  Tetra-phenyl-methane      ......     C  \  ^^5. 

C6H5 

1  CCH5 

All  these   hydrocarbons  are  known,  and  the  derivatives  of 
tri-phenyl-methane  are  of  special  interest  and  importance. 
There  is  one  reaction  by  means  of  which  these  hydrocarbons 


314  DI-PHENYL-METHANE,    ETC. 

can  be  made  very  readily.  It  has  also  been  used  for  the  synthe- 
sis  of  many  other  hydrocarbons.  It  depends  upon  the  remark- 
able fact  that,  when  a  hydrocarbon  is  brought  together  with 
a  compound  containing  chlorine,  and  aluminium  chloride  then 
added,  hydrochloric  acid  is  evolved,  and  union  of  the  two 
substances  is  effected,  the  aluminium  chloride  not  entering  into 
the  composition  of  the  product.  Thus,  when  benzene  and 
benzyl  chloride,  C6H5.CH2C1,  are  brought  together  under  ordi- 
nary circumstances,  no  action  takes  place  ;  but,  if  some  solid 
aluminium  chloride  be  added,  reaction  takes  place  in  the  sense 
of  the  following  equation  :  — 

C6H5.CH2C1  +  C6H6  =  C6H5.CH,.C6H5  +  HC1, 

Di-phenyl-methane. 

and  di-phenyl-methane  is  formed. 

Similarly,  when  chloroform  and  benzene  are  brought  together 
in  the  presence  of  aluminium  chloride,  tri-phenyl-inethane  is 
formed  according  to  this  equation  :  — 

CHC13  +  3  C6H6  =  CH(C6H5)3  +  3  HC1. 

Tri-phenyl-methane. 

Another  method  by  which  these  hydrocarbons  can  be  made, 
consists  in  heating  a  chloride  and  a  hydrocarbon  together  in  the 
presence  of  zinc  dust.  Thus,  benzyl  chloride  and  benzene  give 
di-phenyl-methane  when  boiled  with  zinc  dust ;  and  benzal 
chloride,  C6H5.CHC12,  and  benzene  give  tri-phenyl-me thane  :  — 

C6H5.CHC12  +  2  C6H6  =  CH(C6H5)3  +  2  HC1. 
Only  tri-phenyl-methane  will  be  considered. 

Tri  -  phenyl  -  methane,  C19H]6  [  =  CH  ( C(jH5 )  3] .  —  This  hy- 
drocarbon may  be  made,  as  above  described,  from  benzal 
chloride  and  benzene,  and  from  chloroform  and  benzene.  It 
may  be  made  also  from  benzal  chloride  and  mercury  diphenyl, 

Hg(C6H5)2:- 

C6H5.CHC12  +  Hg(C6H5)2  =  CH(CCH5)3  +  HgCl2. 


ANILINE   DYES.  315 

It  forms  lustrous,  thin  laminae,  which  melt  at  92°.  It  is 
insoluble  in  water  ;  easily  soluble  in  ether  and  chloroform.  It 
is  crystallized  best  from  alcohol. 

Towards  reagents  it  is  very  stable.  Thus,  ordinary  concen- 
trated sulphuric  acid  does  not  act  upon  it.  r  C6H5 

1   C1  TT 

Oxidizing  agents  convert  it  into  tri-phenyl-carbiuol,  C  •<  n6   5- 

C6H5 

I  OH 

That  the  oxidation-product  is  really  tri-phenyl-carbinol  appears 
probable,  from  the  fact  that  whenever  aromatic  Irydrocarbons 
which  contain  paraffin  residues  are  oxidized,  the  paraffin  resi- 
dues are  first  attacked,  while,  as  a  rule,  the  benzene  residue  is 
unacted  upon. 


\  r  TT  /Mn  ,  r    <~<-mr  TT  xro  t  i     • 

f    U^MjaiJNUshL^^^^-n^-Nt-MsJ,     IS 


Trinitro  -  triphenyl  - 

methane, 

formed  by  treating  tri-phenyl-methane  with  nitric  acid  ;  and 
also  by  treating  a  mixture  of  mtro-benzene  and  chloroform 
with  aluminium  chloride  :  — 

CHC13  +  3  C6H5.NO2  =  CH(C6H4.NO2)3  +  3  HC1. 

This  reaction  shows  that  in  the  tri-nitro  product  one  nitro  group 
is  contained  in  each  benzene  residue. 

Triamido-triphenyl-methane,  para-leucaniline, 

C19H13(NH,)3[>  CH(C6H4  .  NH,)3]. 

The  tri-amido  compound  is  made  by  reduction  of  the  tri-nitro 
compound,  and  also  by  reduction  of  para-rosaniline.  It  is 
converted  into  para-rosaniline  by  oxidation. 

ANILINE  DYES. 

The  well-known  substances  included  under  the  head  of  Ani- 
line Dyes  are  more  or  less  simple  derivatives  of  the  two 
compounds  called  rosaniline  and  para-rosaniline. 

VtHien  mixtures  of  aniline  and  toluidine  are  heated  together 
with  different  oxidizing  agents,  such  as  arsenic  acid,  stannic 


316  DI-PHENYL-METHANE,   ETC. 

chloride,  mercuric  chloride,  etc.,  several  substances  are  formed, 
the  principal  of  which  are  the  two  above  named.  Para-rosani- 
line, C19H17N3,  is  formed  from  para-toluidine  and  aniline,  accord- 
ing to  the  equation,  — 

2  C?H7N  +  C7H9N  +  3  O  =  C]9H17N3  +  3  H2O. 

Aniline.  Toluidine.  Para-rosaniline. 

Rosaniline,  C2oH19]S"3,  is  formed  in  a  similar  way  :  — 
C6H7N  +  2  C7H9N  +  3  O  =  C20H19N3  +  3  H2O. 

Aniline.  Toluidine.  Rosaniline. 

The  composition  and  modes  of  formation  of  the  two  sub- 
stances show  that  rosaniline  is  a  homologue  of  para-rosaniline, 
the  relation  between  the  two  substances  being  represented  by 
the  formulas  C19H17N3  and  C19H16(CH3)N3. 

By  treating  para-rosaniline  with  a  reducing  agent,  it  is  con- 
verted into  para-leucaniline,  which  has  been  shown  to  be  tri- 
amido-triphenyl-methane  :  —  ^  C  II  NH 

Ci9H17N3  +  H2  =  C19H19N3<  =  C  •< 

Para-rosani-  Para-leuc-  \ 

line.  aniline.     \  ^  jj 

We  see  thus  that  para-rosaniline  and  rosaniline,  which  are 
the  fundamental  compounds  of  the  group  of  aniline  dyes,  are 
derivatives  of  the  hydrocarbon  tri-phenyl-methane. 

Para-rosaniline,  Ci9HnN3.  —  The  formation  of  this  sub- 
stance by  oxidation  of  para-leucaniline  and  of  a  mixture  of 
toluidine  and  aniline  was  mentioned  above.  It  is  probably 
one  of  the  constituents  of  the  commercial  dye  known  as  ftich- 
sine.  The  relation  between  para-rosaniline  and  para-leucaniline 
is  probably  expressed  by  the  following  formulas  :  — 

C6H4.NH2 


fC6H5  fC6H4.NH2  fC6H4.NH 

CH  J  C6H5   CH  <{  CCH4.NH2   C(OH)     C6H4.ISTH 


CCH5  cfiH4.NH2  C6H4.NH2 


2        

f  '  i-i      rvi  ui  ( 


C6H4 
Nil 


Tri-phcnyl-  Para-leucaniline.  Triamido-triphenyl- 

methanc.     '  carbiaol.  Para-rosauiline. 


BOSANILINE.  317 

According  to  this,  para-rosaniline  is  an  anhydride  of  triamido- 
triphenyl-carbinol,  somewhat  of  the  same  order  as  oxindol,  which 
is  an  anhydride  of  ortho-amido-a-toluic  acid  (see  p.  293)  :  — 

CH2.CO.OH     p  TT  ^  CH2      ^^         p  yj       CH2.CO 

°     CH 


Ortho-amido-a-toluic  acid.  Oxindol. 

Brosaniline,  C2oHi9N3.  —  This  is  the  principal  constituent  of 
commercial  fuchsine.  It  is  formed  by  oxidizing  a  mixture  of 
aniline  and  toluidine  :  — 


C6H7N  +  2  C7H9N  +  3  O  =  C^H^  +  3  H2O. 

Experiment  78.  In  a  dry  test-tube  put  a  little  dry  mercuric 
chloride  and  a  few  drops  of  commercial  aniline.  Heat  over  a  small 
flame.  Dissolve  the  product  in  alcohol,  with  the  addition  of  a  little 
hydrochloric  or  acetic  acid.  The  beautiful  color  of  the  solution  is 
due  to  the  presence  of  the  hydrochloride  or  acetate  of  rosaniline. 

On  the  large  scale,  the  oxidizing  agent  used  is  arsenic  acid. 
Care  is  taken  to  remove  all  arsenic  acid  from  the  product,  but 
it  is  nevertheless  sometimes  found  in  the  products  obtained  in 
the  market.  Rosaniline  crystallizes  in  needles  or  plates.  It  is 
very  slightly  soluble  in  water  ;  more  readily  soluble  in  alcohol. 
It  forms  three  series  of  salts  with  monobasic  acids.  With  hy- 
drochloric acid  it  forms  the  salts  C2oH19N3.HCl  and  C2oH19N3.3  HC1. 
The  former  is  the  substance  known  as  fuchsine,  though  some  of 
the  fuchsine  met  with  in  the  market  is  the  acetate  of  rosaniline, 
C2oH19N3.  021^02.  Fuchsine  and  the  other  salts  of  rosaniline 
dye  wool  and  silk  directl}'.  For  dyeing  cotton  cloth,  however, 
a  mordant  is  necessary. 

Dyeing.  Animal  fibres,  in  general,  are  colored  directly  by 
dyes  ;  that  is  to  sa}T,  they  have  the  power  of  forming  with  the 
dyes  stable  compounds  which  adhere  to  the  fibres.  This  is  not 
true  of  vegetable  fibres,  as  cotton  cloth  and  linen.  Hence,  in 
order  to  dye  the  latter,  something  must  be  added  of  such  a 
character  that,  with  the  dye,  it  forms  a  compound  which  adheres 
to  the  fibres.  Substances  which  act  in  this  way  are  called 


318  DI-PHENYL-METHANE,    ETC. 

mordants.  Among  the  substances  used  as  mordants  are  alu- 
minium acetate,  ferric  acetate,  and  some  salts  of  tin. 

Experiment  79.  Make  a  dilute  solution  of  picric  acid  by  dissolv- 
ing 2%  to  3s  in  200CC  to  300CC  water.  In  a  portion  of  it  suspend  a  few 
pieces  of  white  yarn  or  flannel.  The  woollen  material  will  be  strongly 
died  yellow.  In  another  portion  suspend  a  piece  of  ordinary  cotton 
cloth.  And  in  a  third  portion  introduce  a  piece  of  cotton  cloth  which 
has  been  soaked  in  aluminium  acetate  and  afterwards  partly  dried. 
The  aluminium  acetate  may  be  made  by  treating  a  solution  of  sugar 
of  lead  with  enough  of  a  solution  of  alum  to  precipitate  the  lead,  and 
then  fllteiiug  off  the  lead  sulphate.  The  unprepared  cotton  cloth, 
when  removed  from  the  picric  acid  solution  and  washed,  will  be  found 
to  be  only  slightly  colored ;  whereas,  that  piece  which  was  soaked  in 
the  mordant  will  be  found  to  be  strongly  dyed.  Similar  experiments 
may  be  made  with  fuchsine. 

Among  the  simpler  aniline  dyes  are  the  following :  — 
Hofmanris  Violet.      This  is  either  the  hydrochloric  acid  01 
acetic  acid  salt  of  tri-methyl-rosaniline.     It  is  made  by  heating 

»•  J  '        O 

together  a  salt  of  rosaniline,  methyl  iodide,  methyl  alcohol,  and 
caustic  potash. 

Iodine  Green  is  the  iodide  of  penta-methyl-rosaniline. 

Aniline  Blue  is  tri-phenyl-rosaniline,  C2oH]6(C6H5)3N3,  which  is 
formed  by  heating  salts  of  rosaniline  with  an  excess  of  aniline. 

PHTHALE'INS. 

In  speaking  of  phthalic  anhydride,  it  was  stated  that  when 
this  substance  is  treated  with  phenols,  phthalems  are  formed ; 
and,  in  speaking  of  resorcin,  a  markedly  fluorescent  body  was 
mentioned  as  being  formed  when  phthalic  acid  and  resorcin  are 
heated  together. 

Phenol-phtlialein,  C,oHl4O4.  —  This  substance  is  formed  by 
treating  a  mixture  of  phenol  and  phthalic  anyhdride  with  sul- 
phuric acid  or  some  other  delrydrating  agent :  — 

2  C6H60  +  C8H408  =  CsoHjA  +  H20. 

Phenol.  Phthalic  Phenol- 

anhydride.  phthalei'n. 


PHTHALE1NS.  319 

The  fused  mass  is  dissolved  in  caustic  soda,  and  the  phenol- 
phthalei'n  precipitated  by  the  addition  of  an  acid.  It  forms  a 
granular  crystalline  powder.  Its  solution  in  alkalies  is  red  or 
violet,  according  to  the  thickness  of  the  layer.  Acids  destroy 
the  color.  Hence  it  is  used  as  an  indicator  in  alkalimetry  as  a 
substitute  for  litmus. 

Phenol-phthalein,  like  rosaniline,  is  a  derivative  of  tri-phenyl- 
methane,  as  has  been  shown  by  the  following  somewhat  compli- 
cated reactions  :  — 

The  chloride  of  phthalic  acid,  or  phthalyl  chloride,  C8H4O2C12, 
when  treated  with  benzene  in  the  presence  of  aluminium  chloride, 
gives  up  its  two  atoms  of  chlorine,  and  in  their  place  takes  up 
two  phenyl  groups,  thus  :  — 

C8H402C12  +  2  C6H6  =  C8H402(C6H5)2  +  2  HC1. 

Phthalyl  chloride.  Diphenyl-phthalide. 

The  substance  thus  formed  is  known  as  diplienyl-phtlialide. 
Its  conduct  towards  water  and  bases  is  such  as  to  show  that  it 
is  the  anhydride  of  an  acid  :  — 

C8H402(C6H5)2  +  H20  =  C8H603(C6H5)2 

or  C7H50  j  C°2H 

1  (C6H5)2 

When  this  acid  is  reduced  by  means  of  zinc  dust  it  loses 

oxygen : — 

(  rc\  TT  (  rc\  IT 

+ 


And,  finally,  when  the  last  product  is  distilled  with  baryta,  it 
loses  carbon  dioxide  and  yields  tri-phenyl-methane  :  — 


(C6H5)2 
We  have  thus  passed  from  phthalic  anhydride  to  tri-phenyl- 


320  DI-PHENYL-METHANE,   ETC. 

methane,  and  the  reactions  just  referred  to  are  in  all  probability 
correctly  represented  by  the  following  formulas  and  equations  :  — 

c  C6H5 

TT  n    _    P  J     ^G"5 

J\  C6H4.C02H. 
O  -  1  ^OH 

Diphenyl-phthalide,  or  an-  Triphenyl-carbinol- 

hydride  of  triphenyl-car-  carbonic  acid. 

binol-carbonic  acid. 

C6H5 

e5  =  C     CfiH5  + 

C6H4.C02H  I  C6H4.C02H 

OH 

Triphenyl-methane- 
carbonic  acid. 


H 

Tri-phcnyl-methane. 

Now,  by  making  dinitro-diphenyl-phthalide,  reducing  it,  and 
boiling  the  diazo  compound  with  water,  the  product  is  phenol- 
phthalei'n.  Hence,  the  latter  compound  appears  to  be  the  di- 
hydroxy  derivative  of  diphenyl-phthalide  :  — 

fC6H5  rCGH4.NH2  r  C6H4  .OH 

c   I  C6H5  c  I  C6H4  .  NH2         c  I  C6H4  .OH 

'   )  C6H4.CO          ")  C6H4.CO  ]  C6H4.CO 

LO  —  i  ^o  —  '  ^o  —  i 

Phenol-phthalei'n. 

The  formula  for  phenol-phthalem  may  also  be  written  thus  :  — 
CCH4  .OH      c      C6H4      CQ 
C6H4.OH  O 

the  curious  arrangement  of  the  carbonyl  group  being  simply  the 
sign  of  the  anhydride  condition  between  carboxyl  and  hydroxyl, 
of  which  the  simplest  expression  is 


FLUOKESCEIN.  321 

NOTE  FOR  STUDENT.  —  Although  the  reactions  above  briefly  de- 
scribed may  at  first  sight  appear  to  be  difficult  to  comprehend,  they 
are  in  reality  simple  enough.  The  student  is  earnestly  recommended 
not  to  slight  them  on  account  of  the  long  names  and  complex  formulas 
involved.  They  afford  an  excellent  example  of  the  methods  upon 
which  we  rely  for  determining  the  nature-  of  complex  substances. 
Notice  that  all  appears  dark  until  the  well-known  substance  tri-phenyl- 
methane  is  obtained,  which  suggests  that  all  the  substances  are  deriva- 
tives of  this  fundamental  hydrocarbon ;  and  how  easily,  when  this 
conception  has  once  been  formed,  the  interpretation  of  all  the  reactions 
follows. 

Among  the  other  phthalei'ns  which  deserve  special  mention  is 
that  which  is  formed  with  resorcin. 


Fluorescein,  resorcin-phthale'in,  C2oH12O5. — This  beau- 
tiful substance  is  formed  by  simply  heating  together  resorcin 
and  phthalic  anhydride  :  — 

2  C6H4(OH)2  +  C8H403  =  CsoHjA  +  2  H2O. 

Its  solutions  in  alkalies  are  wonderfully  fluorescent.  The  sub- 
stance, which  is  sold  under  the  name  "  uranin"  for  the  purpose 
of  exhibiting  the  phenomenon  of  fluorescence,  is  an  alkaline  salt 
of  fluorescein. 

The  reaction  which  takes  place  between  resorcin  and  phthalic 
anhydride,  when  fluorescein  is  formed,  is  of  the  same  kind  as 
that  which  takes  place  between  phenol  and  the  anhydride  to 
form  phenol-phthalein.  We  would  therefore  expect  to  find  that 
fluorescein  is  expressed  by  the  formula 

r      (OH 


PTT     (OH 

6    3(OH 
C6H,.CO 

O ' 


322  DI-PHENYL-METHANE,    ETC. 

which  shows  its  analogy  to  phenol-phthalei'n, 

f  C6H4.OH 

I  C6H,.OH 

J\  C6H4.CO 

LO- 

It  is  found,  however,  that  in  reality  fluorescem  corresponds  to 
the  above  formula  less  one  molecule  of  water  ;  and  it  is  believed 
that  the  water  is  given  off  as  represented  thus  :  — 


fC6H1o 


(OH 

=   C20H12O5. 
C6H4.CO 

o — ' 

Fluorescei'n. 

Eosin,  tetra-brom-fluorescein,  C2oH8Br4O3,  is  formed  by 
treating  fluorescem  with  bromine.  Its  dilute  solutions  have  an 
exquisite,  delicate  pink  color  which  suggests  a  color  often  seen 
in  the  sky  at  the  dawn  of  day.  Hence  the  name  eosm,  from 
^ws,  dawn.  It  is  fluorescent,  and  is  used  as  a  dye. 


CHAPTER   XVII. 
HYDROCARBONS,   CnH2n-8,   AND    DERIVATIVES. 

THE  hydrocarbons  thus  far  considered  are  of  three  classes. 
They  are:  (1)  paraffins,  or  saturated  hydrocarbons  of  the 
marsh-gas  series ;  (2)  unsaturated  hydrocarbons  related  to 
the  paraffins ;  and  (3)  hydrocarbons  which  contain  residues 
of  the  saturated  paraffins  and  of  benzene. 

We  now  pass  to  a  brief  consideration  of  a  hydrocarbon  which 
is  made  up  of  a  residue  of  benzene  and  of  an  unsaturated  par- 
affin. It  bears  to  ethyl ene  the  same  relation  that  toluene  bears 
to  marsh  gas  ;  that  is  to  say,  it  is  phenyl-ethylene. 

Styrene,  phenyl-ethylene,  C8H8(=  C6H5.CH.CH2).  —  This 
hydrocarbon  is  contained  in  liquid  storax, — a  fragrant,  honey- 
like  substance  which  exudes  from  various  plants,  as  the  liquid- 
amber.  It  is  formed  by  distilling  cinnamic  acid  with  lime  :  — 

C9H802  =  C8H8  +  C02. 

NOTE  FOR  STUDENT.  —  What  does  this  reaction  suggest  with  regard 
to  the  relation  between  cinnamic  acid  and  styrene? 

It  is  also  formed  from  phenyl -ethane,  C6H5.C2H5,  in  the  same 
way  that  ethylene  is  formed  from  ethane  :  — 

|  C2H6  -f-  Br2       =  C2H5Br  +  HBr 

1  C2H5Br  +  KOH  =  C2H4  +  KBr  +  H2O ' 

C6H5 .  C2H5      +  Br2      =  C6H5 .  C2H4Br  +  HBr  ; 
C6H5.C2H4Br  +  KOH  =  C6H5.C2H3      +  KBr  +  H2O. 

Styrene. 


324       HYDROCARBONS,    CnH2n_8,    AND   DERIVATIVES. 

Its  formation   by  heating   acetylene    was    mentioned   on  p. 

o.^o  .  _ 

4  C2H2  =  C8H8. 

NOTE  FOR  STUDENT.  —  What  other  polymeric  product  is  obtained 
by  heating  acetylene? 

Styrene  is  a  liquid  of  an  aromatic  odor  ;  boils  at  144°  to 
144.5°;  insoluble  in  water  ;  iniscible  with  ether  and  alcohol  in 
all  proportions. 

When  heated  alone  up  to  300°,  or  even  when  allowed  to  stand 
at  ordinary  temperatures,  it  is  converted  into  a  polymeric  modi- 
fication, called  meta-styrene,  which  is  a  solid.  This  same  change 
is  readily  effected  by  several  reagents,  such  as  iodine  and  con- 
centrated sulphuric  acid.  Styrene  unites  directly  with  chlorine 
and  bromine  in  the  same  way  that  etlrylene  does  (see  p.  212)  :  — 


Chromic  acid  and  other  oxidizing  agents  convert  styrene  into 
benzoic  acid  (see  remarks,  p.  246).  Some  higher  members  of 
this  series  have  been  prepared,  such  &$  phenyl-propylene,phenyl- 
Itutylene,  etc.;  but  at  present  they  are  not  of  sufficient  import- 
ance to  make  their  consideration  necessary. 

Styrene  is  closely  related  to  cinnamic  acid,  from  which  the 
interesting  and  important  compounds  of  the  indigo  group  are 
obtained. 

Styryl  alcohol,  C9H10O(=  C6H5.CH.CH  .CH.OH).  —  This 
alcohol  occurs  in  nature  in  the  form  of  an  ethereal  salt  of  cin- 
namic acid  in  liquid  storax,  and  also  in  balsam  of  Peru.  It 
forms  long,  thin  needles,  which  melt  at  33°.  It  boils  at 
250°.  It  takes  up  hydrogen,  and  yields  phenyl-propyl  alcohol, 
C6H5.CH2.CH2.CH2OH  (see  p.  281)  :  - 

C6H5.CH.CH.CH2OH  +  H2  =  C6H5.CH2.CH2.CH2OH. 

By  treatment  with  hydriodic  acid  it  yields  aliyl-benzene 
(phenyl-propylene)  ,  C6H5.CH.CH.CH3,  and  toluene. 


CINNAMIC   ACID.  325 

When  oxidized  with  platinum  black  it  is  converted  into  the 
corresponding  aldehyde,  cinnamic  aldehyde  ;  and,  by  further 
oxidation,  into  cinnamic  acid.  The  relations  between  the  three 
substances  are  the  familiar  ones  of  a  primary  alcohol,  and  the 
corresponding  aldehyde  and  acid  :  — 

C6H5  .CH  .CH  .CH2OH.  C6H5  .CH  .CH  .CHO. 

Styryl  alcohol.  Cinnamic  aldehyde, 

C6H5.CH.CH.CO2H. 

Cinnamic  acid. 

These  compounds  are  simply  the  phenyl  derivatives  of  allyl 
alcohol,  acrolei'n,  and  acrylic  acid  :  — 

CH2.CH  .CH2OH.         CH2.CH  .CHO.         CH2.CH.CO2H. 

Allyl  alcohol.  Acrolei'n  or  Acrylic  acid. 

acrylic  aldehyde. 

Cinnamic  acid,  l 

__          ,  ,.  .,    ( 

Phenyl-acrylic  acid,  > 

Cinnamic  acid  is  found  in  liquid  storax,  partly  in  the  free  con- 
dition, and  partly  in  the  form  of  an  ethereal  salt  in  combination 
with  styryl  alcohol,  as  styryl  cinnamate,  in  the  balsams  of  Tolu 
and  Peru.  It  may  be  made  synthetically  :  — 

1  .  By  heating  together  benzoic  aldehyde  and  acetyl  chloride  :  — 
CGH5.COH  +  CH3.COC1  =  C6H5.C2H2.CO2H  +  HC1. 

This  reaction  will  be  better  understood  by  writing  it  in  two 
equations  :  — 


(1)  C6H5.CH|O!  +  CH2:H.COC1=  C6H5.CH.CH.COC1 

Cinnamyl  chloride. 

(2)  C6H5  .CH  .CH  .COC1  +  H2O  =  C6H5  .CH  .CH  .CO2H  +  HC1. 

Cinnamyl  chloride. 

The  kind  of  action  represented  in  equation  (1)  is  not  un- 
common. We  have  already  met  with  it  in  the  formation  of 
mesitylene  from  acetone  (see  p.  248)  ,  in  which  case  two  hydro- 
gens from  each  of  three  methyl  groups  unite  with  an  oxygen 


326        HYDROCARBONS,    CnH2n_8,    AND   DERIVATIVES. 

atom  from  each  of  the  three  carbonyl  groups.  The  product 
is  called  a  condensation-product,  and  the  action  is  known  as 
condensation. 

2.  By  heating  together  benzoic  aldehyde  and   acetic  anhy- 
dride :  — 

C6H5.COH  +  (C2H3O)20  =  C6H5.C2H2.C02H  +  C2H4O2. 

It  is  probable  that  the  action  between  benzoic  aldehyde  and 
acetic  anhydride  is  of  the  same  kind  as  that  between  the  alde- 
hyde and  acetyl  chloride. 

3.  By  treating  benzal  chloride  with  sodium  acetate  :  — 


C6H5  .CH!C12  +  CiHslH  .CO2Na  =  C6H5  .CH  .CH  .CO2Na  +  2  HC1. 
C6H5.CH.CH.C02Na  +  HC1   =  C6H5.CH.CH.CO2H  +  NaCl. 

The  acid  is  now  manufactured  on  the  large  scale  by  this  last 
method. 

Cinnamic  acid  is  a  solid  which  crystallizes  in  monoclinic 
prisms.  It  melts  at  133°,  and  bolls  at  300°  to  304°.  It  is 
easily  broken  up  into  styrene  and  carbon  dioxide  :  — 

C6H5.CH.CH.C02H  =  C6H5.CH.CH2  +  CO2. 

Oxidizing  agents  convert  it  first  into  benzoic  aldehyde  and 
then  into  benzoic  acid.  Nascent  hydrogen  converts  it  into 
hydro-cinnamic  or  phenyl-propionic  acid,  C6H5.CH2.CH2.C(XH 
(p.  293).  It  unites  with  hydrochloric,  hydrobromic,  and  hydri- 
odic  acids  :  — 

C6H5.C2H2.C02H  +  HC1  =  C6H5.C2H3C1.C02H. 

Phenyl-chlor-propionic 
acid. 

Treated  with  substituting  agents,  such  as  nitric  acid,  etc.,  it 
yields  substitution-products  in  which  the  entering  atoms  or 
groups  are  contained  in  the  benzene  residue,  in  the  ortho  and 
para  positions  relatively  to  the  acrylic  acid  residue,  C2H2.CO2H. 
Bromine  yields  the  addition-product  C6H5.C2H2Br2.CO2H. 


COUMAUIN.  327 


Nitro-cinnamic  acids,   C6H4  {  °2^  2  •C°2H.  —  The  ortho- 

and  para-acids  are  formed  by  dissolving  cinnamic  acid  in  nitric 
acid. 

NOTE  FOR  STUDENT.  —  What  are  the  products  when  toluene  is 
treated  with  nitric  acid?  When  benzoic  acid  is  treated  in  the  same 
way?  To  which  case  is  the  above  analogous? 

Amido-cinnamic  acids,  C6H4{^2'C°2H.  —  These  acids 

are  formed  by  treating  the  nitro-acids  with  reducing  agents  . 
The  ortho-acid  loses  water  when  set  free  from  its  salts,  and 

|~1    Tj 

forms  the  anhydride  carbostyril,  C6H4  <    2   2^C.  OH,  analogous 
to  hydro-carbostyril  (p.  294). 


Coumarin,  C,JI6O.=CGH.i  is  a  compound  found 

in  Tonka  beans,  and  in  some  other  plant-substances.  It  has 
been  made  synthetically  from  salicylic  aldehyde  and  acetic  anhy- 
dride, just  as  cinnamic  acid  is  made  from  benzoic  aldehyde  and 
acetic  anhydride.  The  first  product  of  this  action  is  probably 

f  P  TT    C*OOTT 

ortlio-liydroxy-cinnamic  acid,  or  coumaric  acid,  C6H4  <    2   2  '  , 

which  then  loses  water,  yielding  the  anhydride  or  coumarin. 
Coumarin  has  a  pleasant  odor,  like  that  of  vanillin,  and  is  used 
for  flavoring.  Treated  with  bases,  it  yields  salts  of  coumaric 
acid. 


CHAPTER   XVIII. 
PHBNYL-ACBTYLBNB   AND    DERIVATIVES. 

Phenyl-acetylene,  acetenyl-benzene,  C6H5.C.CH,  bears 
to  acetylene  the  same  relation  that  styrene,  or  phenyl-ethylene, 
bears  to  ethylene.  It  is  made  from  styrene  in  the  same  way 
that  acetylene  is  made  from  ethylene  :  — 

(1)  C2H4  +Br2         =  C2H4Br2; 

(2)  C2H4Br2  +  2  KOH  =  C2H2          +  2  KBr  +  2  H2O. 

C6H5  .C2H3       +  Br2         =  C6H5  .C2H3Br2 ; 
C6H5.C2H3Br2  +  2  KOH  =  C6H5.C2H  +  2  KBr  +  2  H2O. 

Phenyl-acetylene. 

It  is  a  liquid  which  boils  at  139°  to  140°.  It  unites  directly  with 
four  atoms  of  bromine,  forms  metallic  derivatives,  and,  in  gen- 
eral, conducts  itself  like  acetylene  (which  see). 

Phenyl-propiolic  acid,  CaH6O2(=  C6H5.C.C.CO2H).— This 
acid  is  a  carboxyl  derivative  of  phenyl-acetylene,  bearing  to  it 
the  same  relation  that  cinnamic  acid  bears  to  phenyl-ethylene. 
It  is  made  from  cinnamic  acid,  by  treating  brom-ciunamic  acid, 
C6H5 .  C2HBr .  CO2H,  with  alcoholic  potash  :  - 

C6H5.C2HBr.CO2H  =  C6H5.C2.CO2H  +  HBr. 

It  forms  long  needles,  which  melt  at  136°  to  137°.  When 
heated  with  water,  it  breaks  up  into  carbon  dioxide  and 
phenyl-acetylene . 

Ortho-nitro-phenyl-propiolic  acid,  CeH^  j  ^Q  o  ,  is 
made  from  ortho-nitro-cinnamic  acid,  in  the  same  way  that 
phenyl-propiolic  acid  is  made  from  cinnamic  acid  (see  pre- 


INDIGO   AND    ALLIED    COMPOUNDS.  329 

ceding  paragraph).  It  is  of  special  interest,  for  the  reason 
that  it  can  easily  be  transformed  into  indigo.  The  trans- 
formation is  most  readily  effected  by  boiling  it  with  alkalies 
and  grape  sugar,  or  some  other  mild  reducing-agent.  The 
reaction  is  represented  by  the  following  equation :  — 

2  C6H4  {  % !•  C02H  +  H4  =  Cl6H10N202  +  2  CO2  +  2  H2O. 

<•  -NO2(°]  Indigo> 

Ortho-nitro-phenyl- 
propiolic  acid. 

The  acid  is  at  present  manufactured  on  the  large  scale,  for 
the  purpose  of  making  indigo. 


INDIGO  AND  ALLIED  COMPOUNDS. 

In  several  plants,  Indigofera  tinctoria,  Isatis  tinctoria,  etc., 
there  occurs  a  glucoside  called  indican,  which,  under  the  influ- 
ence of  dilute  mineral  acids  and  certain  ferments,  breaks  up, 
yielding  indigo-blue  and  a  substance  resembling  the  glucoses. 
The  indigo  of  commerce  is  prepared  in  the  East  and  West 
Indies,  in  South  America,  Egypt,  and  other  warm  countries. 
At  the  proper  stage  the  plants  are  cut  off  down  to  the  ground, 
put  in  a  large  tank,  and  covered  with  water.  Fermentation 
takes  place,  the  indican  breaking  up  and  yielding  indigo,  as 
above  stated.  The  liquid  becomes  green,  and  then  blue. 
When  the  fermentation  is  finished,  the  liquid  is  drawn  off 
into  a  second  tank.  This  liquid  contains  the  coloring-matter 
in  solution.  In  contact  with  the  air  it  is  oxidized,  forming 
indigo,  which,  being  insoluble,  is  thrown  down.  In  order  to 
facilitate  the  precipitation  of  the  indigo,  the  liquid  is  thoroughly 
stirred.  Finally,  the  liquid  is  drawn  off,  the  precipitated  indigo 
pressed  and  dried,  and  then  sent  into  the  market. 

The  substance  prepared  as  above  has  a  dark-bine  color.  It 
contains  other  coloring-matters  besides  indigo-blue.  Its  value 
depends  upon  the  amount  of  the  definite  compound,  iudigo-blue, 
which  it  contains. 


330  PHENYL-ACETYLENE   AND   DERIVATIVES. 

Indigo-blue,  indig-otin,  C16H10N2O2.  —  Indigo-blue  is  ob- 
tained from  commercial  indigo  by  reducing  it  to  indigo-white, 
and  then  exposing  the  clear  colorless  solution  to  the  air,  when 
indigo-blue  is  precipitated. 

Experiment  8O.  Into  a  test-tube  put  a  small  quantity  of  powdered 
indigo ;  add  fine  zinc  filings  or  zinc  dust  and  caustic  soda.  When  the 
mixture  is  heated  the  indigo  forms  a  colorless  solution.  When  this 
result  has  been  reached,  pour  some  of  the  solution  into  a  small  evapo- 
rating-dish.  Contact  with  the  air  colors  it  blue. 

Indigo-blue  may  be  made  artificially  by  a  number  of  methods, 
among  which  the  two  following  are  the  principal  ones  :  — 

1.  By  boiling  ortho-nitro-phenyl-propiolic  acid  (which  see) 
with  an  alkali  and  grape  sugar :  — 

2  C02. 

2.  By  heating  isatine  (which  see)  with   phosphorus  trichlo- 
ride, phosphorus  and  acetyl  chloride. 

Without  going  into  the  mechanism  of  these  reactions,  we  see 
that  there  are  two  general  ways  of  obtaining  indigo  artificially. 
The  first  starts  from  cinnamic  acid,  which  is  successively  con- 
verted into  ortho-nitro-cinnamic  acid  and  ortho-nitro-phenyl- 
propiolic  acid ;  the  second  starts  from  benzoic  acid,  which  is 
converted  into  ortho-nitro-  and  ortho-amido-benzoic  acids.  The 
latter  is  then  converted  successively  into  the  chloride,  cyanide, 
and  corresponding  -acid,  the  anhydride  of  which  is  isatine.  For 
fuller  details  of  the  reactions  involved  in  the  formation  of  ortho- 
nitro-ph3nyl-propiolic  acid,  see  p.  328  ;  and  for  similar  details 
in  regard  to  isatine,  see  p.  289.  As  has  been  stated,  indigo  is 
now  manufactured  on  the  large  scale  by  the  first  of  the  two 
methods  above  given. 

Indigo-blue  cr}rstallizes  from  aniline  in  dark-blue  crystals. 
It  sublimes  in  rhombic  crystals.  Its  vapor  has  a  purple-red 
color.  It  is  insoluble  in  water,  alcohol,  and  ether ;  soluble  in 
aniline  and  chloroform.  Oxidizing  agents  convert  it  into  isa- 


INDIGO-WHITE.  331 

tiiie  (which  see).  Heated  with  solid  caustic  potash,  it  yields 
carbon  dioxide  and  aniline  ;  boiled  with  a  solution  of  caustic 
potasli  and  finely-powdered  black  oxide  of  manganese,  it  is 
converted  into  ortho-amido-benzoic  acid  (anthranilic  acid)  (see 
p.  289). 

A  great  many  compounds  related  to  indigo  have  been  made, 
of  late  years,  incidentally  to  the  study  of  its  chemical  conduct. 
The  synthesis  of  indigo  has  been  effected,  as  a  result  of  this 
stud}'.  The  work  undertaken  was  suggested  by  the  few  funda- 
mental facts,  above  stated,  that  indigo  when  decomposed  readily 
yields  aniline  and  ortho  -  amido  -  beuzoic  acid.  The  question 
which  investigators  have  endeavored  to  answer  is,  What  rela- 
tions do  indigo-blue  and  the  compounds  allied  to  it  bear  to 
ortho-amido-benzoic  acid?  Although,  as  far  as  indigo-blue  is 
concerned,  this  has  proved  to  be  a  difficult  question,  to  which  a 
definite  answer  is  still  lacking,  as  far  as  some  of  the  simpler 
derivatives  are  concerned  it  has  been  answered.  Two  of  these, 
oxindol  and  isatine,  have  been  considered  in  connection  with 
the  simpler  compounds,  to  which  they  are  most  closely  related. 
A  few  others  will  here  be  mentioned. 

Indigo-white,  OlcHi2N2O2,  is  formed  by  reduction  of  indigo- 
blue,  as  above  described.  Its  solutions  rapidly  turn  blue  in  the 
air,  in  consequence  of  the  formation  of  indigo-blue. 

When  indigo  is  oxidized  with  nitric  acid,  isatine,  CSH5NO2, 
is  formed  :  -  Q^^^  +  O2  = 


When  isatine  is  treated  with   sodium    amalgam,  it   takes   up 
hydrogen,  and  yields  dioxindol,  C8H7NO2  :  — 

C8H5N02    +  H2  =  C8H7NO2. 

Isatine.  Dioxindol. 

B}"  further  reduction,  dioxindol  loses  an  atom  of  oxygen,  yield- 
ing oxindol,  C8H7NO  :  — 

C8H7N02     +  H2  =  C8H7NO  +  H2O. 

Dioxindol.  Oxindol 


332  PHENYL-ACETYLENE   AND   DERIVATIVES. 

The  relations  between  oxindol  and  isatine  cannot  readily  be 
made  clear  without  a  careful  study  of  some  very  complex  re- 
actions. 

It  would  also  lead  too  far  and  be  unprofitable  to  discuss  here 
the  constitution  of  indigo-blue  itself.  Suffice  it  to  say,  that 
it  has  been  shown  to  consist  of  a  doubled  group  very  similar 
to  that  of  oxindol. 


CHAPTER    XIX. 

HYDROCARBONS    CONTAINING    TWO    BENZENE 
RESIDUES    IN    DIRECT    COMBINATION. 

JUST  as  the  marsh-gas  residue,  metlryl,  CH3,  unites  with  methyl 

CH. 
to  form  ethane,    !    \  so  the  benzene  residue,  phenyl,  C6H5, 

CH3  C6H5 

unites  with  phenyl  to  form  the  hydrocarbon,  diphenyl,    I       ,  and 

C6H5 

similar  residues  of  toluene,  and  the  higher  members  of  the  series 
unite  in  a  similar  way  to  form  homologues  of  diphenyl. 

Diphenyl,  C12H]0(=  C6H5  .C6H5). — This  hydrocarbon  is  made 
by  treating  brom-benzene  with  sodium  :  — 

2  C6H5Br  +  2  Na  =  C12H10  +  2  NaBr ; 
and  by  conducting  benzene  through  a  tube  heated  to  redness  :  — 

n   /~1   TT /~1     TT          _|_     TT 

It  forms  large,  lustrous  plates.     It  melts  at  70.5°,  and  boils 
at  254°.     It  is  easily  soluble  in  hot  alcohol  and  ether. 

Diphenyl  is  an  extremely  stable  substance.  It  resists  the 
action  of  ordinary  oxidizing  agents,  but  with  strong  ones  it 
yields  benzoic  acid.  A  large  number  of  derivatives  of  diphenyl 
have  been  studied.  A  curious  one,  known  as  carbazol,  occurs 
in  coal  tar.  This  has  been  shown  to  be  a  substituted  ammonia 
containing  a  residue  of  diphenyl.  It  is  properly  designated  by 
the  name  diphenyl-imide,  and  is  represented  by  the  formula 
C6H4 
I  >NH.  It  has  been  made  synthetically  by  passing  the  vapor 

of  diphenyl  amine,  NHJ  Cr>H3,  through  a  red-hot  tube,  a  reaction 

I  C6^5 


334      HYDROCARBONS    WITH   TWO   BENZENE   RESIDUES. 

taking  place  which  is  analogous  to  that  mentioned  above  as 
taking  place  when  benzene  is  treated  in  the  same  way,  the 
product  in  the  latter  case  being  diphenyl. 

Naphthalene,  C10H9.  —  While  the  relations  of  diphenyl  to 
benzene  are  clearly  shown  by  its  simple  synthesis  from  brom- 
benzene,  the  relations  of  naphthalene  to  benzene  have  been 
discovered  through  a  careful  study  of  its  chemical  conduct. 
The  facts  can  be  best  interpreted  by  assuming  that  the  molecule 
of  naphthalene  is  formed  by  the  union  of  two  benzene  residues 
in  such  a  way  that  they  have  two  carbon  atoms  in  common,  as 
represented  in  the  formulas 

/Cv      /C 
HC-CH-C-CH-CH  HCX    ^C7    ^CH 

I  I  I  and  I  I  I     • 

HC-CH-C-CH-CH  HCX    /C^    /CH 

C  G 

H  H 

How  this  conception  was  formed  will  be  shown  below,  after 
the  properties  and  the  reactions  of  naphthalene  shall  have  been 
considered. 

Naphthalene  is  a  frequent  product  of  the  heating  of  organic 
substances.  Thus,  it  is  formed  by  passing  the  vapors  of  alco- 
hol, ether,  acetic  acid,  volatile  oils,  petroleum,  benzene,  toluene, 
etc.,  through  red-hot  tubes  ;  and,  also,  by  treating  ethylene  and 
acetylene  in  the  same  way.  It  is  therefore  found  in  coal  tar, 
and  is  sometimes  found  in  gas-pipes  used  for  gas  made  by 
heating  naphtha,  gasoline,  etc.,  to  high  temperatures.  It  has 
been  made  synthetically  by  conducting  phenyl-butylene  bromide 
over  highly -heated  lime  :  — 

C6H5.C4H7Br2  =  C4H4.C2.C4H4  +  H2  +  2HBr; 

and  by  conducting  isobutyl-benzene  over  lead  oxide  :  — • 

C6H5.C4H9  +  03  =  C4H4.C2.C4H4  +  3  H2O, 
Neither  of  these  reactions,  however,  is  of  much  assistance 


NAPHTHALENE.  335 

in  enabling  us  to  form  a  conception  in  regard  to  the  nature  of 
naphthalene. 

Naphthalene  is  prepared  on  the  large  scale  from  those  por- 
tions of  coal  tar  which  boil  between  180°  to  220°.  This  material 
is  treated  with  caustic  soda,  and  then  with  sulphuric  acid,  and 
distilled  with  water  vapor. 

It  forms  colorless,  lustrous,  monoclinic  plates.  It  melts  at 
79.2°,  and  boils  at  216.6°.  It  has  a  pleasant  odor;  is  volatile 
with  water  vapor,  and  sublimes  readily.  It  is  insoluble  in  water; 
easily  soluble  in  boiling  alcohol,  from  which  it  may  be  crystal- 
lized. Oxidizing  agents  convert  it  into  phthalic  acid  (see 
Exp.  74). 

The  ease  with  which  naphthalene  yields  phthalic  acid,  sug- 
gests that  the  hydrocarbon  is  probably  a  di-derivative  of  benzene 
containing  two  hydrocarbon  residues  ;  such,  for  example,  as  is 

f     f~*\     TT 

represented  by  the  formula  C6H4  \    2   2      Sucb  a  substance,  how- 


ever,  contains  un  saturated  paraffin  residues,  and  hence  ought 
readily  to  take  up  bromine,  hydrobromic  acid,  etc.  Bromine 
and  chlorine  are  indeed  taken  up  easily,  but  the  products  thus 
obtained  act  rather  like  the  addition-products  of  benzene  than 
the  addition-products  of  the  unsaturated  paraffins.  They  break 
up  readily,  and  yield  stable  substitution-  products  of  naphtha- 
lene ;  and,  further,  the  first  product  of  the  action  of  bromine 
on  naphthalene  is  not  an  addition-product,  but  mono-brom- 
naphthalene,  C10H7Br,  a  fact  which  shows  that  substitution  takes 
place  more  easily  with  naphthalene  than  addition.  We  have 
seen  that  a  hydrocarbon  containing  a  benzene  residue  and  an 
unsaturated  paraffin  residue,  as,  for  example,  styrene  or  phenyl- 
ethylene,  CGH5.C2H3,  and  phenyl-acetylene,  C6H5.C2H,  when 
treated  with  bromine  or  hydrobromic  acid,  takes  them  up  as 
readily  as  ethylene  and  acetylene,  and  this  action  takes  place 
before  substitution.  According  to  this,  naphthalene  ought  to 
take  up  bromine  with  avidity  before  substitution  of  its  hydrogen 
takes  place. 


336      HYDKOCARBONS   WITH   TWO   BENZENE   RESIDUES, 
f  C  TF 

The  formula  C6H4  \    2   2  and  similar  ones  being  thus  rendered 

v  vyrt-t-^2 

extremely  improbable,  the  next  thought  that  suggests  itself  is 
that  the  two  groups  CaH2  may  be  united,  as  represented  in  the 

(CH.CH 
formula  CfiH4 )          I    .     Assuming,  further,  that  the  two  groups 

I  CH.CH 

are  united  to  two  carbon  atoms  of  the  benzene  residue  which 
are  in  the  ortho  relation  to  each  other,  we  may  write  this  same 

formula  thus :  — 

H 
/C 
HCX    XC-CH-CH 

I  !  I 

HCV     /C-CH-CH 

xcr 

H 

or,  what  is  the  same  thing,  — 

H  H 

UC7    ^C/    XCH 

I  I  I 

HO  \       /Ox        /  OH 
\c/      \c/ 

H  H 

This  formula  represents  naphthalene  as  made  up  of  two 
benzene  residues  united  in  such  a  way  that  the}7  have  two 
carbon  atoms  in  common.  This,  as  has  been  stated,  repre- 
sents the  h}7pothesis  at  present  held  in  regard  to  the  nature  of 
naphthalene. 

As  regards  the  assumption  that  the  two  residues  are  united 
through  carbon  atoms  which  are  in  the  ortho  position  relatively 
to  each  other,  it  should  be  said  that  this  assumption  is  made 
because  phthalic  acid  is  the  product  of  oxidation  ;  and  the  facts 
already  considered  have  shown  us  that  terephthalic  acid  must 
be  represented  by  the  formula 


NAPHTHALENE.  337 


CO2H 

C 
HCX    XCH 

I  I 

HC,      /CH 

xcr 

C0H 


and  isophthalic  acid  by 


C02H 
HCX    XCH 


XCC02H 
H 

and  hence,  in  terms  of  the  accepted  hypothesis,  the  third  pos- 
sible formula  must  be  given  to  phthalic  acid ;  viz.,  — 

H 

HCX    XC.CO2H 

I  I 

HCX    7C.CO2H 

H 

Are  there  any  facts  besides  the  few  above  mentioned  which 
make  the  hypothesis  appear  probable? 

There  is  an  ingenious  and  interesting  line  of  reasoning  which 
appears  to  show  that  the  fundamental  notion  involved  in  the 
above  formula  for  naphthalene  is  true.  This  fundamental  notion 
is  that  the  hydrocarbon  consists  of  two  benzene  residues  which 
have  two  carbon  atoms  in  common.  The  facts  which  lead  to 
this  conclusion  are  the  following :  — 

When  nitro-naphthalene  is  oxidized  it  yields  nitro-phthalic 
acid.  This  shows  that  the  nitro  group  is  contained  in  a 
benzene  residue ;  and  we  may  represent  it  by  the  formula 


338      HYDROCARBONS   WITH   TWO   BENZENE   RESIDUES. 

f   ri  TT 

C6H3.NO2]    2   *,  the  oxidation  taking  place  as  indicated  thus  :  — 


C6H3  .  N02       *'  +  90=  C6H3  .  N02          *     +  H2O  +  2  CO2. 


By  reducing  this  same  nitro-naphthalene,  amido-naphthalene 
is  obtained  ;  and,  when  this  is  oxidized,  phthalic  acid  is 
formed  :  — 


C6H4       2    .  NH2  +  12  Q  =  CgH4     CO,H  +  2  Co2+HN08+HaO. 


These  two  reactions  show  (1)  that  the  part  of  nitro- naphtha- 
lene in  which  the  nitro  group  is  situated  is  a  benzene  residue  ; 
(2)  that  there  is  another  benzene  residue  in  the  compound  into 
which  the  nitro  group  has  not  entered. 

It  has  been  noticed,  also,  that  by  oxidation  of  a  naphthalene- 
sulphonic  acid,  both  sulpho-phthalic  and  phthalic  acid  itself  are 
obtained. 

It  follows,  from  these  facts,  that  naphthalene  is  made  up  of 
two  benzene  residues,  and  the  only  way  in  which  a  hydrocarbon 
of  the  formula  C10H8  can  be  thus  made  up,  is  by  having  two 
carbon  atoms  common  to  the  two  residues,  as  represented  in 
the  formula  alreacty  given.  It  cannot  be  made  up  thus  :  — 

H 


HC7    XCH 

XCH 

1             1 

1 

HC\C/C\ 

/CH 

NT 

H 

H 

H 

nor  thus  :  — 


for  neither  of  these  formulas  expresses  the  fundamental  idea  of 


DERIVATIVES   OF  NAPHTHALENE.  339 

the  presence  of  two  benzene  residues  in  the  same  molecule. 
The  only  formula  which  expresses  this  idea  in  terms  of  the 
commonly  accepted  hypothesis  for  benzene  is 

H          H 

HC/  /XCX    XCH 

I  I 

HCV     /C\     /CH 

xcr     xcr 

H          H 

The  proof  just  given  for  this  formula  is  independent  of  any 
notions  regarding  the  ortho,  meta,  and  para  relations  in 
benzene.  As  phthalic  acid  is  the  product  of  oxidation,  it 
follows  that  the  carboxyl  groups  in  the  acid  must  bear  to  each 
other  the  relation  expressed  by  the  formula 

H 

HV/    XC-CO2H 

I  I 

HCX     /C-CO2H 

xcr 

H 

and,  therefore,  that  in  all  ortho  compounds  the  substituting 
groups  bear  this  same  relation  to  each  other.  Hence,  by  start- 
ing with  the  notion  that  the  above  formula  represents  phthalic 
acid, —  and  to  this  notion,  it  must  be  remembered,  we  are  led 
independently  of  any  facts  connected  with  the  formation  of  the 
acid  from  naphthalene,  —  the  accepted  formula  of  naphthalene 
follows  naturally.  And,  on  the  other  hand,  we  are  led,  by  a 
study  of  naphthalene  itself,  to  the  accepted  formula,  and  from 
this  the  above  formula  for  phthalic  acid  follows. 

Derivatives  of  Naphthalene. 

An  interesting  fact  which  has  been  discovered  by  a  study  of 
the  mono-substitution  products  of  naphthalene  is  this, — that 
two,  and  only  two,  varieties  are  known.  There  is  an  a-  and 


340      HYDROCARBONS   WITH   TWO   BENZENP]   RESIDUES. 

a  /?-chlor-naphthalene,  an  a-  and  a  /?-brom-naphthalene,  etc., 
etc.  This  fact  is  quite  in  harmon}'  with  the  views  held 
regarding  the  constitution  of  naphthalene,  as  will  readily  be 
seen  by  examining  the  formula  somewhat  more  in  detail. 
We  see  that  there  are  two,  and  only  two,  kinds  of  relations 
which  the  hydrogen  atoms  bear  to  the  molecule ;  all  those 
marked  with  an  a  being  of  one  kind,  and  all  those  marked 
with  a  /5  being  of  another  kind :  — 

aH          aH 

XC/ 


/^\ 

cr    V 

aH          aH 

Here,  again,  a  problem  presents  itself  like  that  which  was 
considered  in  connection  with  the  bi-substitution  products  of 
benzene.  Our  theory  gave  us  three  formulas,  and  three  com- 
pounds are  known.  The  problem  was,  to'  determine  which 
formula  to  assign  to  each  compound.  Here  we  have  two 
formulas  for  two  brom-naphthalenes  and  other  mono-substi- 
tution products  of  naphthalene,  and  we  actually  have  two 
compounds ;  and  the  question  arises,  which  of  the  two 
formulas  must  we  assign  to  a  given  compound?  The 
method  adopted  is  simple,  and  can  be  explained  in  a  few 
words.  That  nitro  derivative  of  naphthalene  which  is  known 
as  a-nitro-naphthalene  yields  nitro-phthalic  acid  by  oxida- 
tion ;  and  the  relation  of  the  nitro  group  to  the  carboxyl 
groups,  in  this  acid,  has  been  determined.  It  is  expressed 
by  the  formula 


NO 


C-C02H 
I 
C-CO2H 


H 

Formula  I. 


NAPHTHOL.  841 

while  the  formula  of  the  other  nitro-phthalic  acid  is 

H 
7    XC-C02H 


H 

Formula  II. 

As  a-nitro-naphthalene  yields  the  acid  of  formula  I.,  it  fol- 
lows that  in  it  the  nitro  group  must  occupy  the  position  of  one 
of  the  hydrogen  atoms  marked  a  in  the  above  formula  for  naph- 
thalene. Those  substitution-products  of  naphthalene  which 
belong  to  the  same  series  as  a-nitro-naphthalene  are  called  a 
derivatives.  In  the  /?  compounds  the  substituting  group  or 
atom  must  occupy  the  place  of  one  of  the  hydrogen  atoms 
marked  (3. 

Among  the  derivatives  of  naphthalene  are  the  following :  — 

Naphthoic  acid,  C10H7.CO2H,  which  bears  to  naphthalene 
the  same  relation  that  benzoic  acid  bears  to  benzene. 

a-Naphthol,  C10H7  .OH.  — This  compound  is  made  from  naph- 
thalene in  the  same  way  that  phenol  is  made  from  benzene  :  — 

1.  By  treating  a-naphthyl-amine,   C10H7.NH2,  with   nitrous 
acid. 

NOTE  FOR  STUDENT.  —  Write  the  equations. 

2.  By   melting    a-naphthalene-sulphonic    acid   with    caustic 
potash. 

NOTE  FOR  STUDENT.  —  Write  the  equation. 

a-Naphthol  is  a  solid  which  melts  at  96°.  It  has  an  odor 
somewhat  resembling  that  of  phenol.  Its  general  chemical 
conduct  is  much  like  that  of  phenol.  Toward  oxidizing 
agents,  however,  its  action  is  peculiar.  Thus,  when  boil.d 


342      HYDROCARBONS    WITH    TWO   BENZENE   RESIDUES. 

with  potassium  chlorate  and  hydrochloric  acid,  a  di-  chlorine 
substitution-product  is  formed  ;  and  at  the  same  time  a 
second  oxygen  atom  enters,  and  the  product  has  the  char- 
acteristics of  the  quinones  (which  see).  It  is  di-chlor- 
naphtho-quinone.  It  will  be  remembered  that  ordinary 
quinone  is  formed  by  the  oxidation  of  hydro-quinone,  a  di- 
hydroxyl  derivative. 

Some  of  the  substitution-products  of  naphthol  are  used  as 
dyes;  as,  for  example,  dinitro-napkthol,  C10H5(NO2)2OH, 
which  is  known  as  Mar  tins'  s  Yellow;  dinitro-naphthol- 
sulphonic  acid,  C10H4(NO2)2(8O3H).OH,  the  potassium  salt 
of  which,  K2C10H4N2SO8,  is  known  as  Naphthol  Yellow  S. 
With  diazo  compounds,  naphthol  has  a  remarkable  power  of 
combination  ;  and  a  great  many  derivatives  containing  resi- 
dues of  diazo  compounds,  and  of  naphthol  or  its  substitution- 
products,  have  been  made,  and  some  of  them  have  founjl 
application  as  dyes.  The  simplest  compound  of  this  kind-  is 
formed  by  bringing  together  uaphthol  and  diazo-benzene 
nitrate  :  — 
C10H7.OH  +  C6H5-N2-N03  =  C10HG  [  ^T^5  +  HM)3. 


It  is  called  naphtliol-diazo-benzene.  The  dye  known  as  Poir- 
rier's  Orange  II.  is  a  sulphonic  acid  of  naphthol-diazo-benzene, 
and  is  probably  formed  by  treating  diazo-benzene-sulphonic  acid 
with  naphthol. 

Naphtho-quinone,  C10H6O2.  —  This  compound  is  obtained 
by  oxidizing  naphthalene  with  chromic  acid  ;  also  by  oxidiz- 
ing a-amido-a-naphthol  and  other  di-substitution  products  of 
naphthalene  in  which  the  two  substituting  groups  are  in  the 
para  position  relatively  to  each  other.  It  bears  to  naphthalene 
the  same  relation  that  ordinary  quinone  bears  to  benzene  ;  that 
is,  it  is  naphthalene  in  which  two  hydrogen  atoms  are  replaced 
by  two  oxygen  atoms. 

It  forms  yellow  needles,  which  melt  at  125°.     Like  ordinary 


QUINOLINE   AND    ANALOGOUS   COMPOUNDS.  343 

quinone,  it  is  volatile  with  water  vapor.     Hydriodic  acid  con- 
verts it  into  liydro-naplitho-quinone :  — 

C10H<A  +  H2  =  CWH6(OH)2. 

NOTE  FOR  STUDENT.  —  Compare  with  the  action  of  reducing  agents 
on  ordinary  quinone. 

Di-hydroxy-naphtho-quinone,    C10H4|L         ,    is    a    dye 

known  by  the  name  napktkassarin,  on  account  of   its  resem- 
blance to  alizarin  (which  see) . 

Two  homologues  of  naphthalene  —  meth}*l-  and  ethyl-naph- 
thalene—  have  been  prepared.  /2-Methyl-naphthalene  has  been 
found  in  coal  tar. 

QUINOLINE   AND    ANALOGOUS    COMPOUNDS. 

It  has  been  stated,  that,  by  distilling  quinine  and  cinchonine 
with  caustic  potash,  pyridine  and  some  of  its  homologues  are 
obtained.  At  the  same  time  a  base  belonging  to  another  series 
is  formed,  together  with  some  of  its  homologues.  This  base  is 
known  as  quinoline,  to  suggest  its  formation  from  quinine.  It 
has  the  composition  expressed  by  the  formula  C9H7N.  The  next 
two  homolognes  of  quinoline  are  lepidine,  C10H9N,  and  dispo- 
line,  CUHUN.  Three  bases,  isomeric  with  the  three  named, 
have  been  found  in  coal  tar.  These  are  known  as  leucoline, 
iridoline,  and  cryptidine.  We  thus  have  the  two  series  :  — 

BASES  FROM  ALKALOIDS.  BASES  FROM  COAL  TAR. 

Quinoline     .     .     .     C9H7N       .     .     .     Leucoline. 
Lepidine      .     .     .     C10H9N      .     .     .     Iridoline. 
Dispoline     .     .     .     CnHnN     .     .     .     Cryptidine. 


Quinoline,  C9H7N.  —  Quinoline  is  formed  by  the  distillation 
of  quinine,  cinchonine,  or  strychnine,  with  caustic  potash.  It 
is  formed  from  certain  derivatives  of  benzene. 


344      HYDROCARBONS    WITH    TWO    BENZENE   RESIDUES. 

1.  By  passing  allyl-aniline  over  heated  lead-oxide  :  — 

C6H5 .  NH .  C3H5  =  C9H7N  +  4  H. 

2.  By  heating  together  glycerin,  aniline,  and  nitro-benzene  :  — 

(1)  C6H5.N02   +  C3H803  =  C9H7N  +  3  H2O  +  O2 ; 

(2)  C6H5NH2     +  C3H803  =  CgHyN  +  3  H2O  +  H2 ; 

(3)  2  C6H5NH2  +  C6H5N02  +  3  C3H8O3  =  3  C9H7N  +  11  H2O. 

3.  From  di-clilor-quinoline  :  — 

C9H5C12N  +  4  H  =  C9H7N  -f  2  HC1. 

The  last  method  is  the  most  suggestive,  as  it  leads  to  a  defi- 
nite view  in  regard  to  the  relation  between  qu incline  and  ben- 
zene. Di-chlor-quinoline  is  made  by  treating  hydro-carbostyril 
with  phosphorus  pentachloride.  Hydro-carbostyril  is  the  anhy- 
dride of  ortho-hydro-cinnamic  acid.  This  relation  is  partly 
expressed  by  the  formula :  — 

H  H2 

UC/    XCX     XCH2 

I  I  I 

HC          C  CO 

XCX    XNX 
H  H 

The  transformation  of  hydro-carbostyril  into  di-chlor-quino- 
line  takes  place  easily  ;  and  the  reaction  can  be  best  interpreted 
by  assuming  quinoline  to  be  made  up  thus :  — 

H          H 

HC/    XCX     XCH 

I  I  I 

HC-v        /C»\        /OH 
N(T       XNX 
H 

Quinoline  is  thus  regarded  as  formed  from  the  union  of  a 


QUINOLINE.  345 

residue  of  benzene  and  a  residue  of  pyridine,  in  the  same  way 
that  naphthalene  is  believed  to  be  formed  from  two  residues  of 
benzene.  The  formula  suggests  the  existence  of  two  isomeric 
quinolines,  in  one  of  which  the  nitrogen  is  in  the  a  position,  as 
represented  in  the  above  formula,  while  in  the  other  it  is  in 
the  ft  position.  The  bases  from  the  alkaloids  belong  to  the 
a  series  ;  those  from  coal  tar  belong  to  the  ft  series. 

Quinoline  is  a  liquid  which  boils  at  237°.  Potassium  perman- 
ganate converts  it  partially  into  cinchomeronic  acid,  C7H5NO4. 
This  is  a  pyridine-dicarbonic  add,  C5H3N(CO2H)2.  The  for- 
mation of  this  acid  is  analogous  to  that  of  phthalic  acid  formed 
by  oxidizing  naphthalene. 

Quinoline  readily  takes  up  hydrogen,  forming  hydro-quinoline, 
C9H9N,  and  tetra-hydro-qumoUne,  CgHnN.  These,  as  well  as 
the  hydrogen  addition-products  of  pyridine,  are  believed  to  exist 
in  the  alkaloids.  Tetra-hyclro-quinoline  has  been  found  in  the 
crude  quinoline  obtained  by  distilling  cinchonine  with  caustic 
soda. 

Many  derivatives  of  quinoline  have  been  made.  Substitution- 
products  are  obtained  by  treating  nitro-products  of  substituted 
benzene  with  glycerin  and  aniline. 

A  sulphonic  acid  is  obtained  by  treatment  of  quinoline  with 
sulphuric  acid.  From  this,  liydroxy-quinoline,  G,H6(OH)N,  has 
been  obtained.  Hydroxy-quinoline,  like  quinoline  itself,  takes  up 
Ir^drogen,  forming  tetra-Jiydro-hydroxy-quinoline,  C9H10.OH.N. 
Finally,  by  treating  this  compound  with  methyl  iodide,  methyl 
is  introduced,  and  a  product  obtained  which  is  called  hydro- 
metlioxy -quinoline :  — 

C9HnON  -f  CH3I  =  C10H13NO  +  HI. 

This  substance  resembles  quinine,  and  its  hydrochloric  acid 
salt  is  used  in  medicine  to  some  extent  as  a  substitute  for 
quinine.  The  salt  is  known  as  kairine. 


CHAPTER    XX. 

HYDROCARBONS    CONTAINING   TWO   BENZENE 
RESIDUES    INDIRECTLY  COMBINED. 

DIPHENYL  and  naphthalene  have  been  shown  to  consist  of  two 
benzene  residues  in  direct  combination.  Diphenyl-methane  is 
an  example  of  a  hydrocarbon  consisting  of  two  benzene  resi- 
dues in  indirect  combination,  C6H3  .  CH2  .  CSH5.  As  diphenyl- 
methane  is  closely  related  to  toluene,  it  was  considered  in 
connection  with  the  hydrocarbons  of  the  benzene  series. 
There  are  some  hydrocarbons  which  have  been  shown  to 
consist  of  two  benzene  residues  united  by  means  of  resi- 
dues of  unsaturated  paraffins.  The  most  important  of  these 
is  the  well-known  anthracene. 

Anthracene,  CUH10.  —  Anthracene  is  formed  under  condi- 
tions similar  to  those  which  give  rise  to  the  formation  of 
naphthalene,  especially  by  heating  organic  substances  to  a 
high  temperature,  and  is  hence  found  in  coal  tar. 

It  has  been  made  synthetically  from  benzene  derivatives 
by  a  number  of  methods  :  — 

1.  By   passing    benzyl-toluene,    C6H3  .  CH2  .  C6H4  .  CH3,    over 
heated  lead  oxide  :  — 

C14H14  -f  20  =  C14H10  4-  2H20. 

2.  By  heating  benzyl-phenol  with  phosphorus  pentoxide  :  — 
2C6H3.CH2.C6H4(OH)  =  C14H10  +  C6H6  +  C6H5(OH)  +  H2O. 

3.  By  heating  ortho-brom-benz}^!  bromide  with  sodium  :  — 


2  C6H4  +  4  Na  =  CiAo  +  4  NaBr  +  2  H  . 


ANTHRACENE.  347 


C6H4  C6H4  +  4  NaBr  -f  2  H. 


Anthracene  is  prepared  in  large  quantity  from  those  portions 
of  coal  tar  which  boil  between  340°  and  360°.  The  distillate 
is  redistilled,  and  that  which  remains  in  the  retort  after  thy 
temperature  has  reached  350°  is  crystallized  from  xylene.  It 
is  then  crystallized  from  alcohol,  and  finally  sublimed.  It  is 
difficult  to  get  it  in  perfectly  pure  condition.  The  color  may 
be  removed  by  dissolving  the  substance  in  benzene,  and  expos- 
ing it  to  direct  sunlight.  It  forms  laminae,  or  monoclinic  plates, 
which  are  fluorescent.  It  melts  at  213°,  and  boils  above  360°. 

Anthracene  takes  up  hydrogen,  forming  di-hydro-anthracene, 
C14H12,  and  hexa-hydro-anthracene,  C14H16.  It  takes  up  bromine 
and  chlorine,  forming  first  addition-products,  and  then  substi- 
tution-products. 

Oxidizing  agents  convert  anthracene  into  anthm-quinone, 
C14H8O2,  just  as  they  convert  naphthalene  into  naphtha- 
quinone. 

The  formation  of  anthracene  from  ortho-brom  -benzyl-bro- 
mide (see  above)  furnishes  strong  proof  in  favor  of  the  view 
that  anthracene  consists  of  two  groups,  C6H4,  united  by  the 
group  C2H2  ;  thus,  C6H4  .  C2H2  .  C6H4.  It  hence  appears  as  a 
diphenylene1  derivative  of  ethane,  C2H2(C6H4)2,  analogous  to 
diphenyl-ethane,  C2H4(C6H5)2.  This  conception  may  also  be 
expressed  thus  :  — 

H  H 

HC7    XC-CH-CX    XCH 

!  Ill  I 

HC  \       /  C  —  CH  —  C  \      /  CH 

\c/  \c/ 

H  H 

This  is  the  formula  commonly  accepted  for  anthracene.     It  is 

1  Phenylene  =  C0H4. 


348      HYDROCARBONS   WITH   TWO   BENZENE   RESIDUES. 

in  harmony  with  a  large  number  of  facts,  and  has  been  an 
efficient  aid  in  investigations  on  anthracene  and  its  derivatives. 

Anthraquinone,  C14HsO/=  C6Ht  <         >  G^- — Anthra- 


quinone  is  formed  by  direct  oxidation  of  anthracene :  — 
C14H10  +  03  =  C14H802  +  H20. 

The  simplest  synthesis  of  anthraquinone  that  has  been  ef- 
fected consists  in  distilling  calcium  phthalate.  It  is  believed 
that  the  reaction  which  takes  place  is  analogous  to  that  which 
takes  place  when  the  calcium  salt  of  a  monobasic  acid  is  distilled. 
As  is  well  known,  in  the  latter  case  a  ketone  containing  one 
carbonyl  group  is  formed ;  and  it  is  believed  that  the  product 
formed  in  the  distillation  of  calcium  phthalate  contains  two 
carbonyl  groups,  and  that  it  is  a  representative  of  a  class  of 
bodies  which  may  be  called  diketones.  The  subject  of  diketones 
was  briefly  discussed  under  the  head  of  Quinones  (which  see) . 
The  equation  representing  the  formation  of  anthraquinone  from 
calcium  phthalate  is  here  given :  — 
C  !CO6~~~^r> 

1  CO'O  ro 

v        •       i  _  r\  TT  ^•^U^r'TT    j_  v  r*<*nr\ 

—  M^'-M  "^  r^c\  -^  ^fr"*  ~r~  •"  \ja\j\J§* 


Experiment  81.  Dissolve  10s  commercial  anthracene  in  50CC  to 
75CC  glacial  acetic  acid.  Add  20s  powdered  potassium  bichromate. 
Boil  until  the  solution  is  dark  green,  and  then  add  water.  Anthra- 
quinone is  precipitated.  Filter  off,  wash,  dry,  and  sublime. 

Anthraquinone  forms  rhombic  crystals.  It  sublimes  in  yellow 
needles ;  is  insoluble  in  water,  but  slightly  soluble  in  alcohol 
and  ether.  It  is  an  extremely  stable  compound,  resisting  the 
action  of  alcoholic  potash  and  oxidizing  agents.  Melted  with 
solid  potassium  hydroxide,  it  yields  benzoic  acid  :  — 

C14H8O2  +  2  KOH  =  2  C7H5O2K  ; 

C6H4  <  "  >  C6H4  +  2  KOH  =  2  C6H5  .COOK. 


ALIZARIN.  349 

Reducing  agents  convert  it  successively  into  oxantJiranol, 
C14H10O2,  anthranol,  C14H10O,  and  anthracene,  C^Hjo.  These 
changes  may  be  represented  thus  :  — 


Oft  <        >  C6H4  +  H2  =  C6H4  <  >  C6H4  ; 

Oxanthranol. 

rnvnm  C(OH) 

C6H4  <  ^  L)  >C6H4  +  H2  =  C6H4<  ,  >C6H4  +  H2O  ; 

CH 

Antbranol. 

C6H4<  £(OH)   >C6H4  +  H2  =  C6H4<  |     >C6H4  +  H2O. 

CH 

When  heated  with  zinc  dust,  it  yields  anthracene.  A  great 
many  derivatives  of  anthraquinone  have  been  made.  Among 
the  best  known  are  the  hydroxyl  derivatives,  some  of  which 
are  much-prized  dyes  which  are  manufactured  in  great  quan- 
tities. 

The  hydroxyl  derivatives  of  anthraquinone  may  be  made  by 
melting  either  the  bromine  derivatives  or  the  sulphbnic  acids 
with  caustic  potash. 


Alizarin, 
Di-hydroxy-anthraquinone, 


}CUH804[=C14H602(OH)2]. 


Alizarin  is  the  well-known  dye  which  is  obtained  from  madder 
root.  The  substance  found  in  the  root  is  ruberythric  acid,  a 
glucoside  of  the  formula  C^H^Ou.  When  this  is  treated  with 
dilute  acids  or  alkalies  or  ferments,  it  is  decomposed,  yielding 
alizarin  and  a  glucose  :  — 

C2oH22On  =  C14H8O4  -f-  CfjHjgOtf  -f-  H2O. 

Alizarin.  Glucose. 

It  is  formed  by  melting  dichlor-  or  dibrom-anthraquinone  or 
anthraquinone-disulphonic  acid  with  caustic  potash  :  — 

C14H602(S03K)2  +  2KOH  =  C14H6O2(OH)2  +  2  K2SO3. 
Alizarin  is  now  manufactured  from  anthracene  on  the  large  scale, 


350      HYDROCARBONS    WITH   TWO   BENZENE   RESIDUES. 

and  large  tracts  of  land  which  were  formerly  used  for  culti- 
vating madder  are  now  used  for  other  purposes. 

Experiment  82.  Dissolve  20£  anthraquinone  in  a  small  quan- 
tity of  fuming  sulphuric  acid,  heating  gradually  to  160°.  Dissolve  the 
product  in  a  litre  of  water.  Neutralize  with  finely-powdered  chalk ; 
filter.  Precipitate  with  a  solution  of  sodium  carbonate ;  filter ;  and 
finally  evaporate  to  dryness.  The  salt  thus  obtained  is  impure  sodium 
anthraquinone-disulphonate.  In  a  silver  (or  iron)  crucible  melt  this  for 
half  an  hour,  with  potassium  hydroxide,  at  a  temperature  not  above 
270°.  The  formation  of  alizarin,  during  the  melting  of  the  salt  with 
caustic  potash,  is  shown  by  the  dark-purple  color  of  the  mass.  When 
a  little  of  this  is  dissolved  in  water,  it  should  form  a  beautiful  purple- 
red  solution.  Continue  the  melting  until  the  mass  acts  in  this  way. 
Dissolve  the  mass  in  f1  to  I1  water,  and  acidify.  Alizarin  is  thrown 
down  in  brown  amorphous  flakes.  Filter  off,  dry,  and  sublime  between 
watch-glasses. 

Alizarin  forms  red  needles,  which  melt  at  289°  to  290°.  It 
dissolves  in  alkalies,  forming  dark  purple-red  solutions.  When 
heated  with  zinc  dust,  it  yields  anthracene.  It  was  this  reaction 
which  gave  the  first  clue  to  the  nature  of  alizarin,  and  led,  soon 
after,  to  its  synthesis. 

Some  compounds,  isomeric  with  alizarin,  and  also  derived 
from  anthracene,  are  known. 

Purpurin,  )  _ 

f  GUH8<J5  =  LOHHstMOHJaJ . 
Tri-hydroxy-anthraqumone,  > 

Purpurin  is  contained  in  madder  root,  and  is  therefore  found 
in  madder  alizarin.  It  may  be  made  by  melting  alizarin-sul- 
phonic  acid  with  caustic  potash,  and  also  by  melting  tri-brom- 
anthraquinone  with  caustic  potash. 

Anthrapurpurin,  isopurpurin,  Ci4H5O2(OH)3,  is  found  in 
artificial  alizarin. 


Phenanthrene,  CuHi0,  which  is  isomeric  with  anthracene,  is 
also  found  in  the  higher  boiling  parts  of  coal  tar.     The  chemical 


PHENANTHRENB.  351 

conduct  of  this  hydrocarbon  has  led  to  the  conclusion  that  it 
consists  of  two  benzene  residues  directly  united,  as  in  diphenyl, 
C6H5— C6H5 ;  and  that  a  further  connection  between  the  benzene 
residues  is  established  through  a  group  —  CH  =  CH  — ,  thus 
giving  as  the  expression  of  the  structure  the  formula 

C6H4 — 

I  I 


CHAPTER    XXL 
GLUCOSIDES,  ALKALOIDS,  ETC.  -CONCLUSION. 

UNDER  the  head  of  the  sugars,  reference  was  made  (see  p. 
178)  to  a  class  of  bodies  called  glucosides,  which  occur  in 
nature  in  the  vegetable  kingdom.  These  bodies  break  up 
under  the  influence  of  dilute  acids  or  ferments  into  sugar  and 
other  bodies.  Thus,  salicin  breaks  up,  according  to  the  equa- 

tiOD  C6H4(OH)CH2(OC6Hn05H  H2O 

=  C6H12O6  +  C6H4(OH)CH2OH 

Dextrose.  Salicylic  alcohol. 

into  dextrose  and  salicylic  alcohol,  the  alcohol  corresponding 
to  salicylic  acid.  Some  of  the  more  important  glucosides  are 
mentioned  below. 

Aesculin,  Ci5Hi6Oa  +  14  H2O,  occurs  in  the  bark  of  the 
horse-chestnut  tree  (Aesculus  Hippocastanum)  .  It  breaks  up 
into  dextrose  and  aesculetin  :  — 

C15H16O9  +  H2O  =  C6H12O6  -j-  C9H6O4. 

Aesculin.  Dextrose.          Aesculetin. 

Its  water  solution  shows  blue  fluorescence. 


Amygdalin,  OsoH^NOu  +  3  H2O,  occurs  particularly  in  bit- 
ter almonds  ;  also,  in  the  kernels  of  apples,  pears,  peaches, 
plums,  cherries,  etc.  With  emulsin,  which  is  an  aqueous 
extract  of  almonds,  amygdalin  is  broken  up  in  benzoic  alde- 
hyde, rrydrocyanic  acid,  and  dextrose  :  — 

u  +  2  H2O  =  C7H6O  +  CNH  +  2 


Tannins.  —  Under  this  head  are  included  a  large  number  of 
substances,  some  of  which  are  glucosides.     They  all  give  either 


SALICIN.  353 

a  blue  or  a  green  color  with  ferric  salts.  They  have  a  bitter, 
astringent  taste  ;  are  precipitated  by  solutions  of  gelatin  ;  pre- 
cipitate solutions  of  inetals,  and  absorb  oxygen  in  alkaline 
solution.  They  also  unite  with  animal  membranes,  forming- 
compounds  which  resist  the  putrefactive  forces,  thus  tanning 
them,  or  converting  them  into  leather.  Reference  has  already 
been  made  to  gallo-tannic  acid,  which  breaks  up  into  gallic  acid 
and  glucose. 

Helicin,  Ci3H16O7  +  f  H2O,  is  formed  by  the  oxidation  of 
salicin  (which  see) .  It  has  also  been  made  artificially  by  mix- 
ing an  alcoholic  solution  of  acetochlorhydrose  with  the  potassium 
compound  of  salicylic  aldehyde  :  — 

C6H7C105(C2H30)4  +  C7H502K  +  4  C2H6O 
=  C13H1607  +  KC1  +  4C2H5.C2H302. 

Acetochlorhydrose  is  formed  by  heating  dextrose  with  an 
excess  of  acetyl  chloride. 

Helicin  breaks  up  into  dextrose  and  salicylic  aldehyde. 

Indican,  C26H31NO17,  occurs  in  woad.  It  yields,  among 
other  products,  dextrose  and  indigo  blue  :  — 

C26H31N017  +  2  H20  =  3  C6H1006  +  C8H5NO. 

Indigo  blue. 

Myronic  acid,  C10H19NS2O10,  is  found  in  the  form  of  the 
potassium  salt  in  black  mustard  seed.  When  treated  with 
myrosin,  which  is  contained  in  the  aqueous  extract  of  white 
mustard  seed,  potassium  myronate  is  converted  into  dextrose, 
allyl  mustard  oil,  and  potassium  bisulphate  ;  — 

C10H18NS2010K  =  CeHiA  +  C3H5.NCS  +  KHSO4. 

Salicin,  C13H18O7,  occurs  in  willow  bark,  and  in  the  bark  and 
leaves  of  poplars.  •  Its  decomposition  into  salicylic  alcohol  and 
dextrose  has  been  referred  to  (see  preceding  page) . 


354  ALKALOIDS. 

Saponin,  C32H54O18,  is  found  in  soap  root  (Saponaria  offici- 
nalis)  .  Its  water  solution  forms  a  lather  like  that  formed  by 
soap.  This  property  is  frequently  utilized  for  the  purpose  of 
giving  to  "  soda  water"  the  appearance  of  effervescence. 

ALKALOIDS. 

The  alkaloids  are  compounds  occurring  in  plants,  frequently 
constituting  those  parts  of  the  plants  which  are  most  active 
when  taken  into  the  animal  body.  They  are  hence  sometimes 
called  the  active  principles  of  the  plants.  Many  of  these  sub- 
stances are  used  in  medicine.  As  regards  their  chemical  char- 
acter, they  are  basic  in  the  sense  that  ammonia  is  basic  ;  they 
contain  nitrogen,  and  form  salts,  just  as  ammonia  does,  i.e.,  by 
direct  addition  to  the  acids.  These  and  other  facts  lead  to  the 
belief  that  the  alkaloids  are  related  to  ammonia  —  that  they  are 
substituted  ammonias.  Recently  it  has  been  shown  that  several 
of  the  alkaloids  are  related  to  pyridine  (see  p.  307)  and  quino- 
line  (see  p.  343).  Only  a  few  of  the  more  important  alkaloids 
need  be  mentioned  here. 

Alkaloids  of  Peruvian  Baric. 

Quinine,  CaoH-^NaOa  +  3  H2O.  —  This  valuable  substance  is 
obtained  from  the  outer  bark  of  the  Cinchona  varieties.  When 
oxidized,  it  yields  derivatives  of  pyridine.  In  view  of  the 
interest  connected  with  quinine,  the  discovery  of  its  relation  to 
pyridine  and  quinoline  has  led  to  a  large  number  of  investiga- 
tions on  the  derivatives  of  these  two  bases,  and  it  is  probable 
that  before  long  it  will  be  possible  to  make  quinine  synthetically 
in  the  laboratory. 

The  salts  of  quinine  are  formed  by  direct  addition  of  the  base 
to  the  acids.  Thus,  we  have 


Quinine  hydrochloride       .     C^H^^Og  .  HC1  ; 
Quinine  nitrate  ....     C2oH24N2O2  .  HNO3  ; 
Quinine  sulphate     .     .     .     C^H^NgOs  .  H2SO4,  etc.,  etc. 


PIPEKINE.  355 

Cinchonine,  C19H,,N2O,  cinchonidine,  C19H22N2O,  and 
other  bases  occur  with  quinine  in  Peruvian  bark. 

Cocaine,  C17H21NO4,  is  found  in  cocoa  leaves  (Erythroxylon 
c'>ca) .  Very  little  is  known  regarding  its  chemical  nature.  Its 
hydrochloric  acid  salt,  C17H21NO4.HC1,  has  recently  come  into 
prominence  in  medicine,  owing  to  the  fact  that  a  small  quantify 
of  its  solution  placed  upon  the  eye  causes  insensibility  to  pain. 

Nicotine,  CJOHUN2,  occurs  in  tobacco  leaves  in  combination 
with  malic  acid.  Potassium  permanganate  converts  it  into 
nicotinic  acid,  which  is  one  of  the  possible  pyridine-monocar- 
bonic  acids. 

Alkaloids  of  Opium. 

Opium  is  the  evaporated  sap  which  flows  from  incisions  in 
the  capsules  of  the  white  poppy  (Papaver  somnifernm),  before 
they  are  ripe.  The  two  principal  alkaloids  contained  in  opium 
are  morphine  and  narcotine. 

Morphine,  CnH19NO3  +  H2O,  is  a  crystallizable  solid  which 
is  difficultly  soluble  in  water,  alcohol,  and  ether.  When  de- 
composed, it  yields  pyridine,  trimethyl-amine,  and  phenanthrene, 
together  with  other  products. 

Narcotine,  C22H23NO7,  has  been  shown  to  contain  three 
methyl  groups,  which  are  split  off,  as  methyl  chloride,  when 
the  substance  is  heated  with  hydrochloric  acid. 

Piperine,  C17HiyNO3,  is  contained  in  black  pepper.  When 
treated  with  alcoholic  potash,  it  breaks  up  into  piperidiue  and 
piperic  acid :  — 

C17H19N03  +  H20  =  C5H1]LN  -f  C12H10O4. 

Piperidine.       Piperic  acid. 


356  CONCLUSION. 

Piperidine,  C5HnN,  which,  as  just  stated,  is  formed  by  the 
decomposition  of  piperine,  has  been  made  synthetically  by  treat- 
ing pyridine  with  nascent  hydrogen  :  — 

C5H5N  +  6  H  =  C5HUN. 

Pyridine.  Piperidine. 

It  may  therefore  be  called  liexa-hydropyridine  (see  p.  309) . 

Strychnine,  C.21H2,N.,(>,,  and  brucine,  C23H26N2O4  +  4  H2O, 

are  two  alkaloids  which  occur  in  nux  vomica. 


In  the  animal  body  occur  a  large  number  of  complicated  sub- 
stances, the  study  of  which,  at  this  stage,  would  hardly  be 
profitable.  Thus,  there  are  the  albumins,  caseins,  and  fibrin  ; 
the  coloring-matters  of  the  blood,  oxyhsemoglobin,  haemoglobin, 
etc.  It  may  be  said  that,  notwithstanding  the  importance  of 
these  substances,  our  knowledge  of  their  chemistry  is  quite 
limited. 

The  study  of  the  composition  of  animal  substances,  such 
as  milk,  urine,  etc.,  and  of  the  relations  of  the  chemical  sub- 
stances occurring  in  the  body  to  the  processes  of  life,  is  the 
object  of  physiological  chemistry.  Without  a  good  knowledge 
of  the  general  chemistry  of  the  compounds  of  carbon,  however, 
the  subjects  treated  under  the  head  of  Physiological  Chemistry 
cannot  be  understood. 


APPENDIX. 


PAGE  165.     After  ninth  line  from  bottom,  insert :  — 

WE  have  seen  that  the  sulphonic  acids  and  carbonic  acids  are 
analogous  ;  that,  for  example,  methyl-sulphonic  acid,  CH3.SO3H, 
is  analogous  to  methyl-carbonic  or  acetic  acid,  CH3.CO2H. 
Now,  just  as  the  hyclroxy-acids  above  considered  are  derived 
from  the  carbonic  acids  by  the  introduction  of  hydroxyl,  so  we 
can  imagine  a  series  of  hydroxy-acids  derived  in  a  similar  way 
from  the  sulphonic  acids.  Only  one  such  acid  is  well  known, 
and  it  alone  need  be  considered.  It  is  — 


Isethionic   acid,   C2H4  <  i^T-tr*   also  kn°wn  as  hydroxy- 

bUs-H. 

ethyl-sulphonic  acid.  In  composition  it  is  analogous  to  the 
hydroxy-propionic  acids.  It  is  prepared  by  passing  sulphur 
trioxide  into  well-cooled  alcohol  or  ether. 


INDEX. 


Acetamide,  195. 
Acetates,  59. 
Acetic  acid,  57. 
Acetic  aldehyde,  46. 
Acetic  anhydride,  Gl. 
Acetone,  70. 
Acetophenone,  305. 
Acetyl  chloride,  61. 
Acetylene,  222. 
Acid,  Acetic,  57. 

Aconitic,  221. 

Acrylic,  218. 

Adipic,  142. 

Alpha-toluic,  292. 

Amido-acetic,  192. 

Amido-benzoic,  289. 

Amido-caproic,  194. 

Amido-cinnamic,  327. 

Amido-formic,  191. 

Araido-isethionic,  194. 

Amido-succinic,  195. 

Angelic,  218. 

Anisic,  303. 

Aspartic,  195. 

Azelaic,  142. 

Barbituric,  204. 

Behenic,  130. 

Benzoic,  283. 

Brassylic,  142. 

Brom-propionic,  131. 

Butyric,  132. 

Capric,  129. 

Caproic,  129. 

Caprylic,  129. 


Acid,  Carbamic,  191. 
Carbolic,  269. 
Carbonic,  156. 
Cerotic,  130. 
Chlor-acetic,  63. 
Chlor-propionic,  131. 
Cimic,  218. 
Cinnamic,  325. 
Citraconic,  221. 
Citric,  174. 
Crotonic,  219. 
Cyan-acetic,  141. 
Cyanic,  83. 
Cyanuric,  84. 
Dibrom-succinic,  172. 
Di-chlor-acetic,  63. 
Erucic,  218. 
Ethylene-lactic,  163. 
Ethylidene-lactic,  161. 
Fermentation     lactic, 

38. 

Formic,  54. 
Fulminic,  102. 
Fumaric,  220. 
Gallic,  304. 
Glyceric,  166. 
Glycocholic,  158. 
Glycolic,  158. 
Glyoxylic,  170. 
Heptoic,  129. 
Hippuric,  291. 
Hydracrylic,  162. 
Hydro-cinnamic,  293. 
Hydrocyanic,  80. 
Hydrosorbic,  218. 
Hydroxy-succinic,  167. 


Acid,  Hyenic,  130. 
Hypogaeic,  218. 
Isethionic,  357. 
Isobutyric,  133. 
Isophthalic,  296. 
Isosuccinic,  146. 
Itaconic,  221. 
Lactic,  160. 
Laurie,  130. 
Leinoleic,  227. 
Male'ic,  220. 
Malic,  167. 
Malonic,  142,  144. 
Margaric,  130. 
Melissic,  130. 
Mellitic,  297. 
Mesaconic,  221. 
Mesitylenic,  293. 
Mesoxalic,  170. 
Mucic,  176. 
Myristic,  130. 
Naphthoic,  341. 
Nitro-benzoic,  288. 
Nitro-cinnamic,  327. 
Nitro  -  phenyl-  propio- 

lic,  328. 
Nonoic,  129. 
Octoic,  129. 
Ole'ic,  219. 
Oxalic,  142. 
Oxaluric,  204. 
Oxybenzoic,  302. 
Palmitic,  134. 
Parabanic,  203. 
Para-oxybenzoic, 


300 


INDEX. 


Acid,  Pelargonic,  129. 

Phenyl-acetic,  292. 

Phenyl-propiolic,  328. 

Phthalic,  295. 

Picric.  272. 

Pimelic,  142. 

Piperic,  355. 

Propiolic,  226. 

Propionic,  131. 

Protocatechuic,  303. 

Prussic,  80. 

Pyrogallic,  277. 

Pyrotartaric,  142,  147. 

Racemic,  172. 

Roccellic,  142. 

Saccharic,  176. 

Salicylic,  298. 

Sarcolactic,  161. 

Sebacic,  142. 

Sorbic,  226. 

Stearic,  134. 

Styphnic,  276. 

Suberic,  142. 

Succinic,  142,  144. 

Sulpho-cyanic,  84. 

Tannic,  304. 

Tartaric,  171. 

Tartronic,  167. 

Taurocholic.  194. 

Teracrylic,  218. 

Terephthalic,  296. 

Tetrolic,  226. 

Toluic,  292. 

Tri-carballylic,  152. 

Tri-cluor-acetic,  63. 

Trimesitic,  246. 

Uric,  205. 

Uvitic,  246. 

Vanillic,  304. 

Valeric,  133. 
Aconitic  acid,  221. 
Acrole'in,  216. 
Acrylic  acid,  218. 

aldehyde.  216. 
Adipic  acid,  142. 
Aesculin,  352. 


Alcohols,  34. 

Di-acid,  136. 

Hex-acid,  153. 

Primary,  122. 

Secondary,  121. 

Tertiary,  124. 

Tetr-acid,  152. 

Tri-acid,  147. 
Aldehyde  ammonia,  48. 
Aldehydes,  46,  128. 
Alizarin,  349. 
Alkaloids,  354. 
Allantom,  205. 
Alloxan,  205. 
Allyl  alcohol,  214. 

isosulpho-cyanate,215. 

mustard  oil,  215. 

sulphide,  215. 
Alpha-toluic  acid,  292. 
Amido-acetic  acid,  192- 
Amido-acids,  190. 
Amido-benzene,  260. 
Amido-benzoic  acids,  289. 
Amido  -  cinnamic    acids, 

327. 

Amido-f ormic  acid,  191 
Amido-toluenes,  261. 
Amygdalin,  352. 
Amyl  alcohols,  126. 
Amylene,  211. 
Angelic  acid,  218. 
Aniline,  260. 

dyes,  315. 
Anisic  acid,  303. 
Anthracene,  346. 
Anthranilic  acid,  289. 
Anthrapurpurin,  350. 
Anthraquinone,  348. 
Anthraquinone-sulphonic 

acids,  349. 
Arachidic  acid,  130. 
Arsenic-methyl  com- 
pounds, 104. 
Asparagine,  198. 
Aspartic  acid,  195. 
Azelaic  acid,  142. 


B. 

Barbituric  acid,  204. 
Behenic  acid,  130. 
Benzal  chloride,  256. 
Benzaldehyde,  281. 
Benzene,  231. 

Dinitro,  259. 

Hexa-chlor,  253. 

hexachloride,  254. 
Benzene-sulphonic    acid, 

266. 

Benzine,  110. 
Benzoic  acid,  283. 

Amido-,  289. 

Hydroxy-,  298. 

aldehyde,  281. 
Benzophenone,  305. 
Benzoyl  chloride,  287. 
Benzyl  alcohol,  279 

cyanide,  287. 
Bibrom-benzene,  254. 
Bitter-almond  oil,  281. 
Biuret,  202. 
Boiling-point,  8. 
Borneo  camphor,  311. 
Borneol,  311. 
Brassylic  acid,  142- 
Brom-ethane,  29. 
Brom-methane,  27. 
Bromoform,  28. 
Brom-propionic  acid,  131 
Brucine,  356. 
Butane,  20,  108, 114. 
Butter,  151. 
Butyl  alcohols,  123. 
Butylene,  211. 
Butyric  acid,  132. 

C. 

Cacodyl,  103. 

compounds,  104. 
Caffeine,  206. 
Camphor,  311. 

Artificial,  311. 
Cane  sugar,  182. 


INDEX. 


361 


Capric  acid,  129. 

Cyanuric  acid,  84. 

Caproic  acid,  129. 

Cymene,  250. 

Caprylic  acid,  129. 

Cymogene,  110. 

Caramel,  183. 

Carbamic  acid,  191. 

D. 

Carbamide,  200- 

Carbamines,  88. 

Dextrin,  189. 

Carbohydrates,  177. 
Carbolic  acid,  269 

Dextrose,  177. 
Di-acetamide,  197. 

Casein,  356. 

Uiazo-benzene  com- 

Cellulose, 185. 

pounds,  262. 

Cerotic  acid,  130 

Di-chlor-acetic  acid,  63. 

Chlor-acetic  acid,  63. 

Dichlorhydrin,  149. 

Chloral,  53. 

Di-cyan-diamide,  199. 

hydrate,  53. 
Chlor-ethane,  29. 

Di-methyl-amine,  95. 
Di-methyl-benzene,  241. 

Chlorhydrin,  149- 
Chlor-methane,  27. 

Di-methyl-carbinol,  127. 
Di-methyl-ethyl-methane*. 

Chloroform,  28. 

116. 

Chlor-propionic  acid,  131. 
Cholic  acid,  194. 

Di-methyl-ketone,  70. 
Di-methyl-phosphine,103. 

Cimicic  acid,  218. 

Di-methyl-xanthine,  206. 

Cinchonidine,  355. 

Dinitro-benzene,  259. 

•Cinchonine,  355. 

Dioxindol,  331. 

Cinnamic  acid,  325. 

Diphenyl,  333. 

Amido-,  327. 

Di-phenyl-methane,  313. 

Nitro-,  327. 

Diphenyl  ether,  271. 

Citric  acid,  174. 

Dipropargyl,  227. 

Coal  tar,  230. 

Dodecane,  108. 

Cocaine,  355. 

Dulcite,  154. 

Collidiue,  307. 

Durene,  231. 

Coumarin,  327. 

Dynamite,  151. 

Creatine,  199. 

Creatinine,  200. 

E. 

Cresols,  274. 

Eosin,  322. 

Crotonic  acid,  219. 

Erucic  acid,  218. 

Cuminic  aldehyde,  283. 

Erythrite,  152. 

Cuminol,  283. 

Ethane,  20,  24. 

Cuminyl  alcohol,  281. 

Ether,  42. 

Cyan-acetic  acid,  141. 

Ethereal  salts,  66. 

Cyan-amides,  199. 

Ethers,  Formation  of,  41. 

Cyanates,  90. 

Ethers,  Compound,  66. 

Cyanic  acid,  83. 

Mixed,  45. 

Cyanides,  86. 

Ethyl  acetate,  68. 

Cyanogen,  79. 

alcohol,  37. 

chlorides  83. 

aldehyde,  46. 

Ethyl  bromide,  29. 

carbamine,  88. 

carbinol,  127. 

chloride,  29. 

cyanide,  86. 
Ethylene,  211. 

chloride,  32. 

cyanide,  145. 

glycol,  136. 

lactic  acid,  164. 
Ethyl  ether,  42. 
Ethylidene  chloride,   32, 

50. 
Ethyl  iodide,  29. 

isocyanide,  88. 

isosulphocyanate,  92. 

mercaptan,  74. 

methyl  ether,  45. 

mustard  oil,  92. 

nitrate,  68. 

phosphate,  68. 

phosphoric  acid,  68. 

sulphate,  68. 

sulphuric  acid,  42,  68. 

F. 

Fats,  151. 

Fatty  acids,  129. 

Fehling's  solution,  180. 

Fermentation,  38. 
Alcoholic,  38. 
Lactic  acid,  38. 

Ferments,  38. 

Ferricyanogen  com- 
pounds, 82. 

Ferrocyanogen  com- 
pounds, 81. 

Flashing-point,  110. 

Fluorescem,  321. 

Formic  acid,  54. 
aldehyde,  46. 

Formula,  constitutional , 
15. 

Formula,  Determination 
of,  12. 

Fruit  sugar,  181. 


362 


INDEX. 


Fuchsine,  317. 

Hyenic  acid,  130. 

Fulminates,  102. 

Hypogaeic  acid,  218. 

M. 

Fulminic  acid,  102. 

Male'ic  acid,  220. 

Fumaric  acid,  220. 

I. 

Malic  acid,  167. 

G. 

Indican,  353. 

Malonic  acid,  142,  144. 

Galactose,  182. 
Gallic  acid,  304. 
Gasoline,  110. 
Glucose,  177. 
Glucosides,  352. 
Glyceric  acid,  166. 
Glycerin,  147. 
Glycine,  158,  192. 
Glycocholic  acid,  158. 
Glycocoll,  192. 
Glycolic  acid,  158. 
Glycols,  136. 
Glyoxylic  acid,  170. 
Grape  sugar,  177. 
Guanidine,  199. 
Guanine,  206. 
Gums,  189. 
Gun  cotton,  186. 

H. 

Indigo,  329. 
Indigo-blue,  330. 
Indigo-white,  331. 
Inversion,  183. 
Invert  sugar,  183. 
lodo-ethaiie,  29. 
lodo-methane,  27. 
lodoform,  28. 
Isatine,  289. 
Isethionic  acid,  357. 
Isobutane,  114. 
Isobutyl  alcohol,  124. 
Isobutyric  acid,  133. 
Isocyanates,  90. 
Isocyanides,  88. 
Isohexane,  117. 
Isomerism,  31. 
Physical,  163. 
Isonitroso  compounds, 
101. 

Malonyl  urea,  204. 
Maltose,  185. 
Mannite,  153. 
Margaric  acid,  130. 
Marsh  gas,  20,  23. 
Melissic  acid,  130. 
Mellitic  acid,  297. 
Melting-points,  8. 
Mercaptans,  74. 
Mercury  ethyl,  105. 
fulminate,  102. 
Mesaconic  acid,  221. 
Mesitylene,  246. 
Mesitylenic  acid,  293. 
Mesoxalic  acid,  170. 
Metaldehyde,  49. 
Metamerism,  31. 
Methane,  20,  23. 
Methyl  alcohol,  34. 
aldehyde,  46. 

Hecdecane,  108. 
Helicin,  353. 
Heptanes,  108. 
Heptyl  alcohols,  128. 
Heptoic  acid,  129. 
Hexanes,  20,  108,  116. 
Hexyl  alcohols,  128. 

Isopentane,  116. 
Isophthalic  acid,  296. 
Isopropyl  alcohol,  120. 
Isopurpurin,  350. 
Isosuccinic  acid,  146. 
Iso-sulpho-cyantes,  91. 
Itaconic  acid,  221. 

amine,  94. 
bromide,  27. 
chloride,  27. 
cyanide,  86. 
iodide,  27. 
Methyl-phenyl  ether,  271. 
Methyl-phosphine,  103. 
Methyl-phosphinic    acid, 

Hexylene,  211. 

103. 

Hippuric  acid,  291. 

Methyl-sulphuric  acid,  68. 

Homology,  20,  108. 

Kerosene,  110. 

Methylene  iodide,  27. 

Hydracrylic  acid,  162. 

Ketones,  70. 

Milk  sugar,  184. 

Hydrazines,  99. 

Morphine,  355. 

Hydro-carbostyril,  294. 

. 

Mucic  acid,  176. 

Hydro-cinnamic  acid,  293. 

Lactic  acids,  160. 

Mustard-oils,  91. 

Hydrocyanic  acid,  80. 

Lactose,  184. 

Myronic  acid,  353. 

Hydroquinone,  276. 

Laurie  acid,  130. 

Myrosin,  353. 

Hydrosorbic  acid,  218. 

Laurinol,  311. 

Ni 

Hydroxy  fatty  acids,  155. 

Leucine,  194. 

. 

Hydroxy  succinic  acids, 

Levulose,  181. 

Naphtha,  110. 

167. 

Lutidine,  307. 

Naphthalene,  334. 

INDEX. 


363 


Naphthols,  341. 

Para  -  oxybenzoic     acid, 

Pyrogallol,  277. 

Naphtlioquinone,  342. 

302. 

Pyrotartaric    acid,    142, 

Narcotine,  355. 

Para-rosaniline,  316. 

147 

Nicotine,  309,  355. 

Para  -  oxybenzoic     acid  , 

Pyroxylin,  186. 

Nitriles,  87. 

302. 

Nitro-benzene,  258. 

Pentanes,  20,  108,  116. 

Q- 

Nitro-benzoic  acids,  288. 

Peiityl  alcohols,  125. 

Quercite,  152. 

Nitro-cellulose,  186. 

Petroleum,  109. 

Quinine,  354. 

Nitro-chloroform,  101. 

Phenanthrene,  350. 

Quinoline,  343. 

Nitro-cinnamic  acids, 

Phenol,  269. 

Quinone,  306. 

327. 

Nitro,  272. 

Nitroform,  101. 

phthale'in,  318. 

R 

Nitrogen,  Estimation,  11. 
Nitro-glycerin,  151. 

Tri-nitro,  272. 
Phenyl  acetate,  271. 

Racemic  acid,  172. 

Nitro-methane,  100. 
Nitroso-compounds,  101. 
Kitro-toluenes,  259, 
Nonane,  108. 

Phenylacetic  acid,  292. 
Phenyl-acetylene,  328. 
Phenyl-acrylic  acid,  325. 
Phenyl-amine,  260. 
Phenyl-ethyl  alcohol,  281. 

ifcCSorciiij  —  10. 
Resorcin-phthale'in,  321, 
Khigolene,  110. 
Roccellic  acid,  142. 
Rosaniline,  317. 

o. 

Phenyl-mercaptan,  273. 

Octane,  108. 

Phenyl-propyl      alcohol, 

. 

Octyl  alcohol,  128. 
Oils,  Drying,  227. 
Olefiant  gas,  211. 
Ole'ic  acid  219. 

281. 
Phosphines,  103. 
Phthalems,  318. 
Phthalic  acid,  294. 

Saccharic  acid,  176. 
Salicin,  353. 
Salicylic  acid,  298. 
Salicylic  aldehyde,  300. 

Ole'in  151. 

anhydride,  295. 

Salicylid,  302. 

Opium  bases,  355. 
Orce'in,  277. 

Picoline,  307. 
Picric  acid,  272. 

Saponification,  69. 
Saponin,  354. 

Orcin,  277. 

Pimelic  acid,  142. 

Sarcosine,  193. 

Oxalates,  144. 

Piperic  acid,  355. 

Sebacic  acid,  142. 

Oxalic  acid,  142. 

Piperidine,  309,  356. 

Secondary  alcohols,  121. 

Oxaluric  acid,  204. 

Piperine,  355. 

Soaps,  135. 

Oxalyl  urea,  203. 
Oxindol,  293. 

Polymerism,  31. 
Primary  alcohols,  122. 

Sodium  ethyl,  104. 
Sorbic  acid,  226. 

Oxybenzoic  acid,  302. 

Propane,  20. 
Propargyl  alcohol,  225. 

Starch,  187. 
Stearic  acid,  134. 

Propionic  acid,  130. 

Stearin,  151. 

P. 

Propyl  alcohol,  120. 

Strychnine,  356. 

Palmitic  acid,  134. 

Propylene,  211. 

Styphuric  acid,  276. 

Palmitin,  151. 

Protocatechuic  acid,  303. 

Styrene,  323. 

Paper,  187. 

Prussic  acid,  80. 

Styryl  alcohol,  324. 

Parabanic  acid,  203. 

Pseudocumene,  249. 

Suberic  acid,  142. 

Para-cyanogen,  80. 

Purpurin,  350. 

Substitution,  26. 

Paraffin,  110. 

Pyridine,  307,  309,  356. 

Succinic  acid,  142,  144. 

Paraffins,  108. 

Pyrocatechin,  275. 

anhydride,  146. 

Paraldehyde,  49. 

Pyrogallic  acid,  277. 

Sugar  of  milk,  184. 

364 


INDEX. 


Sulphocyanic  acid,  84. 
Sulpho-cyanates,  91. 
Sulphonic  acids,  76. 
Sulpho  urea,  204. 
Sulphur  ethers,  75. 

T. 

Tannic  acid,  304. 
Tannin,  304,  352. 
Tartaric  acid,  171. 
Tartronic  acid,  167, 
Taurine,  194. 
Taurocholic  acid,  194. 
Terebenthene,  310 
Terephthalic  acid,  296 
Terpenes,  309. 
Tertiary  alcohols,  124. 
Tertiary   butyl    alcohol, 

124. 

Tetra-chlor-methane,  28. 
Tetra  -  methyl  -  methane, 

116 

Theme,  206. 
Theobromine,  206. 


Thymol,  274. 
Tolu  balsam,  240. 
Toluene,  240. 

Amido,  261. 

Nitro,  259. 
Toluic  acids,  292. 
Toluidines,  261. 
Tolyl  carbinol,  281. 
Tri-acetamide,  197. 
Tri-brom-phenol,  272. 
Tri-carballylic  acid,  152. 
Tri-chlor-acetic  acid,  63. 
Trichlorhydrin,  149. 
Trimesitic  acid,  246. 
Tri-methyl-amine,  96. 
Tri-methyl-carbinol,  127. 
Tri-methyl-phosphine, 

103. 

Tri-methyl-xanthine,  206. 
Tri-nitro-methane,  104. 
Tri-nitro-phenol,  272. 
Tri-nitro-resorcin,  276. 
Tri-phenyl-methane,  314. 
Turpentine,  310. 


TL 

Unsaturated  compounds, 

208. 

Urea,  200. 
Uric  acid,  205. 
Uvitic  acid,  246. 

V. 

Valeric  acids,  133. 
Valylene,  227. 
Vanillic  acid,  304. 
Vanillin,  304. 

W. 

Wood  spirits,  34. 

X. 

Xanthine,  205. 
Xantho'genic  acid,  157. 
Xylenes,  241. 
Xylidines,  262. 

Z. 

Zinc  ethyl,  104. 


PRESSWORK  BY  BERWICK  &  SMITH,   BOSTON. 


SCIENCE. 


Organic  Chemistry: 


An  Introduction  to  the  Study  of  the  Compounds  of  Carbon.  By  IRA  REMSEN, 
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SCIENCE. 


Book  in   Geology. 


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Science,  Williston  Sem.,  Mass*  I  un- 


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David  S.  Jordan,  Pres.  and  Prof 
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it  as  the  only  text-book  in  general  zoology 
yet  published  which  is  fit  fa  be  itsed  in 
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and  the  method  is  admirably  carried  out. 

Nature  (London):  In  consideration 
of  the  pernicious  rubbish  which,  even  yet, 
occasionally  finds  its  way  into  our  own 
elementary  schools  under  the  guise  of  the 
elementary  text-book  of  Science,  it  is  pleas- 
ant to  reflect  upon  the  merits  of  this  work. 

Prof.  Alpheus  Hyatt,  Boston  So- 
ciety of  NatTtrat  History  :  Mr  Colton's 
desire  is  to  cultivate  the  faculty  of  obser- 
vation, and  I  think  he  has  succeeded  in 
producing  a  very  valuable  help  to  the 
teacher  of  manual  science. 


T.  C.  Mendenhall,  Pres.  of  Rose. 
Polytechnic  Institute,  Terre Haute,  Ind. : 
I  am  delighted  with  the  book.  I  think  the 
author  has  struck  "pay-rock''  for  the  de- 
partment of  science. 

R.  Ellsworth  Call,  Prof,  of  Zoology t 
Univ.  of  Missouri:  We  have  had  135 
copies  in  use.  Enthusiasm  has  been 
awakened  by  the  actual  study  of  the  ob- 
jects,— an  enthusiasm  which  has  been 
directed  to  definite  ends  by  this  little 
work.  The  book  deserves,  most  abundant 
success,  and  I  believe  will  receive  it. 

Albert  H.  Tuttle,  Prof,  of  Zoology, 
Ohio  State  Univ.:  It  is  the  most  useful 
book  of  its  kind  ever  published  in  this 
country,  not  only  for  high  school  use,  but 
for  beginners  in  zoology  in  colleges  as  well. 


SCIENCE. 


Elementary  Practical  Physics,  or  Guide  for 

the  Physical  Laboratory.  By  H.  N.  CHUTE,  Instructor  in  Physics,  Ann  Arbor 
High  School,  Mich.  Cloth.  JJJJJ  pages.  Price  by  mail  $22-  Introduction 
price  JJJ. 

T  NTENDED  for  pupils  in  high  and  preparatory  schools  pursuing  the 
1  study  of  physics  experimentally.  It  gives  such  help  as.  they  will 
need  in  readily  devising  and  manipulating  apparatus.  It  embodies 
the  experimental  course  given  each  year  by  the  author  to  pupils  of 
the  eleventh  and  twelfth  grades.  To  avoid  as  far  as  possible  the 
duplication  of  apparatus,  alternative  experiments  are  given  under 
most  subjects,  thus  making  it  possible  for  different  sections  of  pupils 
to  investigate  simultaneously  the  same  question  by  different  methods. 
Special  attention  is  given  to  the  simplification  of  apparatus  without 
detracting  from  its  efficiency.  The  descriptions  of  apparatus  are  very 
complete,  even  to  the  dimensions  of  parts.  These  details,  together 
with  the  large  number  of  illustrations,  will  make  it  possible  for  the 
teacher  and  pupil,  occasionally  aided  by  some  local  mechanic,  to  supply 
themselves  with  much  useful  apparatus  at  a  trifling  expense. 

In  but  few  instances  is  the  pupil  informed  what  the  result  of  his  ex- 
periment should  be  ;  instead,  he  is  told  how  to  guard  against  error,  to 
observe  correctly,  and  to  record  neatly  his  observations,  and  by  sugges- 
tive questions  he  is  put  in  the  way  of  correctly  interpreting  his  work. 

The  book  is  designed  to  supplement  the  text-books  on  physics  in 
general  use,  and  not  to  displace  them,  for  on  them  the  pupil  will  de- 
pend for  definitions  of  terms  and,  in  general,  for  the  exposition  of  prin- 
ciples. It  may  be  asked,  "  Why  not  place  the  ordinary  text-book  in  the 
laboratory  and  let  the  pupil  work  through  the  experiments  there  de- 
scribed ? "  The  main  objection  is  that  the  pupil  is  told  in  every  case 
exactly  what  to  expect,  and  it  generally  happens  that  these  expecta- 
tions are  reported  as  fully  realized,  regardless  of  changes  in  the  con- 
ditions unwittingly  made  by  the  experimenter.  The  unavoidable 
personal  coefficient  of  error  receives  little  or  no  recognition. 

Most  of  the  experiments  described  in  this  Guide  are  quantitative 
in  character,  as  it  is  chiefly  by  careful  measurements  that  physical 
truths  are  reached.  Qualitative  work,  however,  is  not  excluded,  as 
it  is  unquestionably  true  that  knowledge  gained  by  the  head  and  hand 
acting  together  is  much  more  lasting  than  that  acquired  simply  by 
reading  or  by  watching  at  a  distance  the  manipulations  of  a  teacher. 


Guides  for  Science  Teaching. 

"Published  under  the  auspices  of  the  BOSTON  SOCIETY  OF  NATURAL  HISTORY. 

INTENDED  for  the  use  of  teachers  who  desire  to  practically  instnct 
their  classes  in  Natural  History,  and  designed  to  supply  such  informa- 
tion as  they  need  in  teaching  and  are  not  likely  to  get  from  any  other 
source. 

These  Guides  were  prepared  solely  as  aids  to  teachers,  —  not  as 
text-books'.  The  plan  of  teaching  followed  throughout  is  based  upon 
the  assumption  that,  — 

Seeing  is'  the  first  step  on  the  road  to  knowledge ;  that, — 

How  MUCH  the  child  learns  in  his  early  years  is  of  little  importance, 
—  HOW  he  learns,  everything',  that, — 

The  teacher's  work  is  not  to  teach  the  facts,  but  to  lead  the  mind  of 
each  pupil  to  work  out  for  itself  the  simple  physical  problems  witnessed  or 
described,  and  to  cultivate  the  habit  of  observation  and  of  perseverance 
in  investigation. 

The  Series  at  present  consists  of  the  following  numbers  :  — 

I.  Hyatt's  About  Pebbles $  .10 

II.  Goodale's  Few  Common  Plants 15 

III.  Hyatt's  Commercial  and  Other  Sponges    .         .         .     .20 

IV.  Agassiz's  First  Lesson  in  Natural  History        .         .     .20 
V.  Hyatt's  Corals  and  Echiiioderms 20 

VI.     Hyatt's  Mollusca 25 

VII.     Hyatt's  Worms  and  Crustacea    .         .         .         .         .     .25 

XII.     Crosby's  Common  Minerals  and  Rocks     .         .        .     .40 

Cloth     .        .        .     .60 

XIII.     Richards'  First  Lessons  in  Minerals 10 


The  following  books  should  be  on  the  teacher's  desk :  — 

Teachers'  Edition  of  Shaler's  Geology  ....          $1.00 

Teachers'  Manual  to  Sheldon's  History 80 

Hall's  Methods  of  Teaching  History 1.30 

Allen's  History  Topics 25 

Clarke's  How  to  Find  the  Stars 15 

Gustafson's  Foundation  of  Death :  A  Study  of  the  Drink 

Question 1-60 

Palmer's  Temperance  Teachings  of  Science         .        .        .     .50 


UNIVERSITY  OF  CALIFORNIA  LIBRARY, 
BERKELEY 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
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Books  not  returned  on  time  aj&  subject  to  a  fine  of 
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demand  may  be  renewed  if  application  is  made  before 
expiration  of  loan  period. 


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